Spectral states and transient behaviour of a sample of X-ray bursters observed by BeppoSax

傅里叶红外光谱的英文傅里叶红外光谱的英文I. IntroductionInfrared spectroscopy is a common analytical method used for studying the chemical properties of a sample. Fourier transform infrared spectroscopy (FTIR), also known as Fourier transform infrared (FTIR) analysis, is a type of infrared spectroscopy that uses a Fourier transform to obtain the spectral information. In this article, we will discuss the English terminology used for FTIR.II. Basic Terminology1. Infrared spectrum: a representation of the absorption or transmission of infrared radiation as a function of wavelength or frequency2. Spectral range: the range of wavelengths or frequencies measured in the infrared spectrum3. Wavenumber: the reciprocal of wavelength, measured in cm-1 in the FTIR spectrum4. Absorbance: the logarithm of the ratio of the incident radiation to the transmitted radiation, measured in the FTIR spectrum5. Peak: a point on the FTIR spectrum that corresponds to a specific vibrational mode of the sample6. Baseline: the absorption background in the FTIR spectrumIII. Sample PreparationBefore performing FTIR analysis, the sample must be prepared in the formof a thin film or powder to ensure uniformity of the sample.IV. InstrumentationFTIR analysis requires a Fourier transform infrared spectrometer, which consists of a source, interferometer, and detector. The sample is placed in the path of the infrared beam generated by the source and the transmitted or absorbed radiation is measured by the detector. The interferometer is used to obtain the interferogram, which is then transformed into the FTIR spectrum.V. ApplicationsFTIR is used in various fields such as chemistry, pharmaceuticals, and material science. It is commonly used for the identification of unknown compounds, characterization of functional groups, and monitoring of chemical reactions.VI. ConclusionFTIR analysis is a powerful technique for studying the chemical properties of a sample. Understanding the basic terminology and instrumentation used in FTIR is essential for accurate interpretation of the spectral data.。

a r X i v :a s t r o -p h /9906390v 1 24 J u n 1999The H αemission of the spiral galaxy NGC 7479Almudena Zurita (azurita@ll.iac.es ),Maite Rozas(mrozas@ll.iac.es )and John E.Beckman (jeb@ll.iac.es )Instituto de Astrof´ısica de Canarias,38200-La Laguna,Tenerife,SPAINAbstract.We use the catalogue of H ii regions obtained from a high quality continuum-subtracted H αimage of the grand design spiral galaxy NGC 7479,to construct the luminosity function (LF)for the H ii regions (over 1000)of the whole galaxy.Although its slope is within the published range for spirals of the same morphological type,the unusually strong star formation along the intense bar of NGC 7479prompted us to analyze separately the H ii regions in the bar and in the disc.We have calculated the physical properties of a group of H ii regions in the bar and in the disc selected for their regular shapes and absence of blending.We have obtained galaxy-wide relations for the H ii region set:diameter distribution function and also the global H αsurface density distribution.As found previously for late-type spirals,the disc LF shows clear double-linear behaviour with a break at log L Hα=38.6(in erg s −1).The bar LF is less regular.This reflects a physical difference between the bar and the disc in the properties of their populations of regions.1.Observations,data reduction and production of the H ii region catalogue.The observations were made through the TAURUS camera on the 4.2m William Herschel Telescope on La Palma.The detector used was an EEV CCD 7with projected pixel size 0”.279×0”.279.Observing conditions were good,with photometric sky and 0”.8seeing.After standard reduction routines,we obtained the calibrated H αcontinuum-subtracted image (Fig.1)by subtracting an image through a non-redshifted filter to the image obtained through a 15˚A filter with central wavelength equal to the redshifted H αemission from the galaxy and calibrating with observations of standard stars.As a selection criterionTable I.NGC 7479:basic parameters (data from RC3catalogue,except P.A.and i ,both from Laine &Gottesman 1998)to construct the H ii region catalogue we specified that a feature must2Figure1.Representaction of the Hαcontinuum-subtracted image of NGC7479 contain at least nine contiguous pixels,each with an intensity of at least three times the r.m.s noise level of the local background.The r.m.s.noise of the background-subtracted Hαimage is15instrumental counts,which means that lower limits to the luminosity of the detected H ii regions,and to the radius of the smallest catalogued regions are, respectively,log L Hα=37.65erg s−1and≈75pc.The detection and cataloguing of the H ii regions were performed using a new pro-gram developed by C.Heller.The program identifies each H ii region, measures the position of its centre,derives the area in pixels and the flux of each region,integrating all the pixels belonging to the region and subtracting the local background value.We catalogued1009H ii regions in NGC7479,and for all the H ii regions we determined equa-torial coordinate offsets from the nucleus and deprojected distances to the centre(in arcsec)using the inclination and position angles given by Laine&Gottesman(1998)(i=51◦,PA=22◦).In Fig.2we show schematically the positions of the H ii regions in the disc of NGC7479, on a deprojected RA-dec grid centred on the nucleus of the galaxy.3Figure2.Representation of the positions of the measured H ii regions.Symbols show ranges of log L.Coordinates of the centre of the image are R.A.=23h4m 56.64s Dec=12◦19′22.9′′(J2000)2.Luminosity functionsThe full count of H ii regions seen in Fig.2is presented in differential form,as a log-log plot in bins of0.15dex,in Fig.3.The luminosity range in Hαis limited at the high end by the luminosity of the brightest detected region,and at the low end by our criteria for a detection.The limit of completeness is log L Hα=38.0,so that the apparent broad peak in the distribution just below this luminosity is an artefact due to observational selection.The best single linearfit of the data to the points above log L Hα=38,corresponding to a power lawdN(L)=ALαdL,has a gradient-0.83±0.06(i.e.α=-1.83±0.06).We have also carried out a bi-linearfit,based on the evidence that at log L∼38.8there is an apparent change in slope in the LF and we explained it as a manifestation of a transition in the physical properties of the regions, but in those cases the luminosity of the transition was always log L Str∼38.6(∼0.2dex lower than in NGC7479).As NGC7479is a barred4galaxy with unusually strong star formation in the bar,we tested the hypothesis that the differences in the LF might be due to this intense star formation activity under somewhat different physical conditions from those in the disc.To perform this test we constructed separately the LF’s for the H ii regions of the bar and of the disc.The results are shown in Fig.3and the LF’s slopes are in Table II.In the LF for the629H ii regions detected in the disc(Fig.5)the change in slope is cleaner than for the total LF and occurs at log L=38.65±0.15(in erg s−1).The change of slope,accompanied by a slight bump in the LF,has been detected in the seven galaxies so far examined in this degree of detail(see e.g.Rozas,Beckman&Knapen1996,Knapen et al.1993).Adding the value for NGC7479to the set of values previouslyFigure3.Luminosity function for the complete sample of H ii regions from the cata-logue with the best linear(a)and bi-linearfit(b),based on the previous experience with late-type spirals.(c)shows the bi-linearfit for the luminosity function of the H ii regions of the disc;the change in slope is seen at log L Hα=38.65.The luminosity function of the bar(d)is clearly less well-behaved than that for the disc.measured for other galaxies,wefind that the rms scatter in L Str in the5 full set of objects is0.08mag.This low scatter can be explained if the IMF at the high luminosity end of the mass function changes little from galaxy to galaxy,i.e.varies little with metallicity.Another necessary condition is that the rate of emission of ionizing photons from a young stellar cluster rises more rapidly than the mass of its placental cloud, a condition which we have examined observationally(Beckman et al. 1999),and shown to hold.If we look at Fig.3,where the LF for the 380H ii regions of the bar is presented,we can see clearly that the irregularity found in the total LF is due to the incorporation of the H ii regions of the bar in the total LF.Clearly star formation conditions in the bar differ from those in the disc.Table II.Luminosity limits,LF slopes and correlation coefficients for thetwo luminosity ranges(in erg s−1)for the LF for the complete sample ofH ii regions from the catalogue and for the LF of the H ii regions of thedisc.Total LF single linearfit38.1≥log L≤40.5-1.83±0.060.969bi-linearfit38.1≥log L≤38.8-1.33±0.040.97938.8≥log L≤40.5-1.99±0.070.9783.Other Statistical properties.−The integral diameter distribution(number of regions with diameters greater than a given value as a function of diameter) is given in Fig.4a From our own and other published studies it has been found that the diameter distribution of the H ii re-gions can be wellfitted by an exponential of form N(>D)= N o exp(−D/D o)where D o is a characteristic diameter,and N o is an(extrapolated)characteristic value for the total number of regions.From the observations represented in Fig.4a,we obtain the values N o=5000±300and D o=110±2pc(with H o=75km s−1Mpc−1).D o has a value predicted for a galaxy of its mea-sured absolute luminosity according to the observational plot ofD o versus luminosity(Hodge1987).−Theflux density distribution is shown in Fig.4b.It was found by dividing the disc into rings using the values of P.A.and i of6diameter distribution function of all H ii regions of NGC7479.The straight line indicates the bestfit.b.)Flux density distribution of all the H ii regions of NGC7479as a function of the deprojected distance to the centre of the galaxy.the galaxy(Table I).There is a clear trend to lowerflux,with increasing radius,which clearly reflects the standard radial decline in surface density of each major component of this disc galaxy.This underlying radialflux density can befitted by an exponential of form f(r)=B exp(−r/h Hα)from which we derive a value for the Hαscale length,h Hα=(2.4±0.3)kpc.4.Physical properties.Using a distance to NGC7479of31.92Mpc we employed the standard theoretical formula(Spitzer1978)relating the surface brightness of an H ii region with its emission measure(Em),(assuming case B recombination and T∼104K)to calculate the Em of the H ii regions. We performed this for a total of39regions,(22in the disc and the rest in the bar),covering the full range of observed radii and chosen as isolated to minimize the uncertainties in calculating their luminosities due to the overlapping.Results are shown in Fig.5a.In Fig.5b.we show the rms electron density(derived from the Em, <N e>rms=7agree well with those found by Kennicutt 1984and by ourselves (Rozas,Knapen &Beckman 1996)for extragalactic H ii regions.Due to ob-servational selection,these tend to be more luminous and larger than Galactic regions.We also computed the filling factors,using δ=(<N e >rms /N e )2.The implicit model is that an H ii region is internally clumpy,so that the observed flux comes from a high density component,which occupies a fraction δ(filling factor)of the total volume;the rest of the volume is filled with low density gas which makes a negligible contribution to the observed emission line strengths.To calculate δ,we need to know the in situ N e for each region.We have not measured these values for NGC 7479,but have used a “canonical”mean value of 135cm −3obtained by Zaritzky et al.1994for 42H ii regions in a large sample of galaxies.The filling factors for the regions range from 4.3×10−4to 1.5×10−3,a range which coincides well with those found for 4galaxies in Rozas et al.1996b.Values of <N e >rms can also be used to estimate the mass of ionized gas,which range from 3000M ⊙to 1.5×106M ⊙.These physical properties,the emission of Lyman cotinuum photons and the equivalent number of O5V stars required to supply the luminosity of the regions are given in a more detailed paper (Rozas,Zurita &Beckman 1998).1002003004001002003004003456Figure 5.Emission measure versus radius (a.),rms electron density versus radius (b.)for the 39selected H ii regions in NGC 7479.85.ConclusionsThe main results of the present work,where we analyze the statistics and properties of H ii regions in NGC7479are summarized below.−Using a high quality continuum-subtracted Hαimage of the grand-design spiral NGC7479,we have catalogued1009H ii regions.−The slope of the LF agrees broadly with slopes for other galaxies of comparable morphological types.−We have found a change in slope in the LF of the H ii regions of NGC7479that occurs at a luminosity slightly higher(≃0.2 dex)than that found in other galaxies of the same morphological type.Due to the intense star formation in the bar of NGC7479, we decided to construct separately the LF’s for the H ii regions of the bar and of the disc,finding:1.the LF of the disc is in no way different from that found inprevious papers for galaxies of the same morphological type,2.The anomaly in the global LF is thus due to different star for-mation conditions in the bar.This must be due to the effects ofgas dynamical parameters on the stellar IMF,and the physicalconditions in the clouds.−The integrated distribution function of the H ii region diameters can be wellfitted by a exponential function.−The densities,filling factors and masses derived from the luminosi-ties and sizes of a selected set of representative regions,through the range of observed luminosities for NGC7479,are in agreement with those found in the previous literature on extragalactic H ii regions.ReferencesBeckman,J.E.,Rozas,M.,Zurita,A.&Knapen,J.H.1999,AJ,,submittedde Vaucouleurs,G.,de Vaucouleurs,A.,Corwin,H.G.,Buta,R.J.,Paturel,G., Fouqu´e,P.,1991Third Reference Catalogue of Bright Galaxies(RC3),Springer, New YorkHodge,P.W.1976,ApJ,205,728Knapen,J.H.,Arnth-Jensen,N.,Cepa,J.,Beckman,J.E.1993,AJ,106,56 Laine S.&Gottesman S.T.1998,MNRAS,297,1041Osterbrock,D.E.1974,Astrophysics of gaseous nebulae,Freeman,San Francisco Rozas,M.,Beckman,J.E.&Knapen,J.H.1996a,AA,307,735Rozas,M.,Knapen,J.H.&Beckman,J.E.1996b,AA,312,275Rozas,M.,Zurita,A.,Heller,C.H.&Beckman,J.E.,1998,AAS,135,145 Spitzer,L.,1978,Physical Processes in the Interstellar Medium,Wiley,New York Zaritzky,D.,Kennicutt,R.C.&Huchra,J.P.1994,ApJ,420,87。

CCP3SURF ACESCIENCENEWSLETTERCollaborative Computational Project3on Surface ScienceNumber26-January2000ISSN1367-370XDaresbury LaboratoryContents1Editorial1 2Scientific Articles2 3SRRTNet-a new global network124High performance computing164.1Cluster-Computing Developments in the UK (16)4.2New HPC Support Mechanisms (22)5Reports on visits256Meetings,Workshops,Conferences296.1Reports on Bursaries (29)6.2Reports from Meetings (32)6.3Upcoming meetings (34)7Abstracts of forthcoming papers37 8Surface Science Related Jobs40 9Members of the working group43 Contributions to the newsletter from all CCP3members are welcome and should be sent to ccp3@eful Links:CCP3Home Page /Activity/CCP3CCP3Program Library /Activity/CCP3+896 SRRTNet /Activity/SRRTNetDLV /Activity/DLVCRYSTAL /Activity/CRYSTALCASTEP /Activity/UKCPMany useful items of software are available from the UK Distributed Computing Support web site,DISCO /Activity/DISCOEditors:Dr.Klaus Doll and Dr.Adrian Wander,Daresbury Laboratory,Daresbury, Warrington,WA44AD,UK1EditorialThe renewal of CCP3,which is due in the summer,is on all our minds,and this edition of the newsletter reminds us of our aims and achievements.Theflagship project supported by the post-doc is at the heart of the CCP–new programs can be developed which would not get offthe ground otherwise.Over the last three years CCP3has been very lucky to have had Klaus Doll working on the development of analytic gradient methods for the CRYSTAL electronic structure package.This will lead to much more efficient structure optimization,of particular benefit to surface scientists where surface relaxation and reconstructions are so important.Klaus’achievements so far are described in thefirst article,and it is most satisfactory that tests on the CO molecule and bulk MgO have proved successful.The next step is to build in symmetry,to achieve greater computational efficiency,and then the new code can be released.As theflagship in the renewal proposal,the working group has chosen the development of methods to study the electronic structure and physical properties of large clusters.These clusters themselves possess surface-like properties, but at the same time it is proposed to study their interaction with surfaces.Such systems are a topic of active research for several of the members of the working group,both theoretical and experimental,and it is expected that their expertise will contribute greatly to the success of the project.Having Adrian Wander as a permanent member of staffat Daresbury supporting CCP3will lead to very welcome support for the synchrotron radiation community in the development of new surface program packages.In this newsletter he describes developments in SRRTNet,originally an American collaboration for providing sup-port for surface scientists using synchrotron radiation,which is likely to develop into an international collaboration based on the CCP model.Adrian is also in discussion with the Daresbury-based X-ray community with a view to developing new codes for the analysis of near-edge spectra in a wider range of systems than can be tackled at the moment,using the improved self-consistent electron potentials available for complex materials.This work would be based at Daresbury,and will form part of the CCP3collaboration.This issue contains short articles on our visitor programme,and by Ally Chan (Nottingham)and Yu Chen(Birmingham)who received student bursaries for participating in ECOSS-18.Please continue to apply for CCP3support!It is interesting to read in the pieces by Ally and Yu what most impressed them at ECOSS–I was struck by Ally’s comment that surface science has broadened to include nanoparticles and nanowires.Just what we thought in our choice offlagship project next time round.John Inglesfield12Scientific ArticlesAnalytical Hartree-Fock gradients for periodic systemsK.Doll,V.R.Saunders,and N.M.HarrisonCLRC,Daresbury Laboratory,Daresbury,Warrington,WA44AD,UKWe report on the progress of the implementation of analytic gradients in the program package CRYSTAL.The algorithm is briefly summarised and tests illustrate that highly accurate analytic gradients of the Hartree-Fock energy can be obtained for molecules and periodic systems.IntroductionComputational materials science has been a fast growingfield in the last years. This is mainly because methods which were developed earlier(density functional theory,molecular dynamics,Hartree-Fock and correlated quantum chemical meth-ods,Monte Carlo schemes,the GW method,etc)can now be applied to demanding realistic systems due to the increase in computational resources(faster CPUs,par-allelisation,cheaper memory and diskspace).CCP3is a collaboration in the area of surfaces and interfaces where progress de-pends on an interaction between experimental and theoretical approaches.There-fore,codes which provide a better theoretical understanding are important.One of the key issues in surface science is the determination of surface structure and adsorption energetics.From the computational point of view,a fast structural optimisation must be possible.Availability of numerical or analytical gradients facil-itatesfinding a minimum energy structure,and availability of analytical gradients can make optimisation algorithms more efficient.As a rule of thumb,analyticalgradients are about N3times more efficient than numerical gradients(with N beingthe number of variables).Also,for future developments such asfinding transition states,gradients are essential.Analytical gradients in quantum chemistry were pioneered by Pulay who did the first implementation for multicentre basis sets[1].In many molecular codes based on quantum chemistry methods,analytical gradients are now implemented and gradient development has become an important task in quantum chemistry[2,3,4,5].Simi-larly,in solid-state codes such as CASTEP,WIEN,or LMTO,analytic gradients are available.Analytic Hartree-Fock gradients have already been implemented in a code for systems periodic in one dimension[6].CRYSTAL[7,8]was born in Turin and is now jointly developed in Turin and Daresbury.CRYSTAL was initially designed to deal with the exact exchange in and to solve the Hartree-Fock equations for real systems.With the modern versions of the code,density-functional2calculations or calculations using Hybrid functionals such as B3LYP with the ad-mixture of exact exchange are also possible.The target of this project,which began in October1997,was the implementation of analytical gradients in CRYSTAL and in autumn1999,thefirst test calculations on periodic systems were performed.In this article,we try to outline the theory and implementation of analytical gra-dients.We try to keep the mathematics at a minimum;a more formal publication is intended in the near future[9].A very comprehensive summary of the theory underpinning CRYSTAL will appear in the future[10].Total energyFirst,we want to briefly summarise how the total energy is obtained.The total energy consists of•kinetic energy of the electrons•nuclear-electron attraction•electron-electron repulsion•nuclear-nuclear repulsionCRYSTAL,similar to molecular codes such as GAMESS-UK,MOLPRO(Stuttgart and Birmingham),GAUSSIAN,TURBOMOLE,etc,solves the single particle Schr¨o dinger equation and a wavefunction is calculated.The wavefunction is based on crystalline orbitalsΨi( r, k)which are linear combinations of Bloch functionsΨi( r, k)= µaµ,i( k)ψµ( r, k)(1) with the Bloch functions constructed fromψµ( r, k)= gφµ( r− Aµ− g)exp(i k g)(2) g are direct lattice vectors, Aµdenotes the coordinate of the nuclei.φµare the basis functions which are Gaussian type orbitals.For example,an s-type function centred at R a=(X a,Y a,Z a)is expressed asφ(α, r− R a,n=0,l=0,m=0)=φµ( r− R a)= Nexp(−α( r− R a)2).In molecular calculations,no mathematical problem arises from any of the interac-tions.In periodic systems,however,there are several divergent terms which have to3be dealt with:for example,in a one dimensional periodic system with lattice con-stant a and n being an index numerating the cells,the electron-electon interaction per unit cell would have contributions like:∞n=1e2na(3)This sum is divergent(similarly in two and three dimensions).Therefore,an indi-vidual treatment of this term is not possible.Instead,all the charges(nuclei and electrons)are partitioned and a scheme based on the Ewald method is used to sum the interactions[11].The Hartree-Fock equations are solved in terms of Bloch functions because the Hamiltonian becomes block-diagonal(i.e.at each k-point the equations are solved independently).The wavefunction coefficients aµ,i are optimised due to this procedure and the total energy can be evaluated.For the computation of gradients,the dependence of the total energy on the nuclear coordinates must be analysed.There are three dependencies of the total energy on the nuclear coordinates:•nuclear-nuclear repulsion and nuclear-electron attraction:obviously,the coor-dinates of the nuclei enter•wavefunction coefficients(or density matrix):we will obtain a different solution with different density matrix when moving the nuclei•basis functions:the basis functions are centred at the position of the nu-clei and therefore moving the nuclei will change integrals over the basis func-tions.These additional terms are called Pulay forces.They are missing when the Hellmann-Feynman theorem is applied and therefore Hellmann-Feynman forces often differ substantially from energy derivative forces in the case of a local basis set(see[1]and references therein).Density matrix derivatives are difficult to evaluate.However,for the solution of the Hartree-Fock equations,this problem can be circumvented and instead a new term is introduced,the so-called energy-weighted density matrix which is easily evaluated [12].However,this is only strictly correct for the exact Hartree-Fock solution. In practice,convergence is achieved up to a certain numerical threshold(e.g.a convergence of10−6E h of the total energy corresponding to27.2114×10−6eV).For very accurate gradient calculations,it may be necessary to make this threshold even lower.The remaining main problem is to generate all the derivatives of the integrals. In a second step,these derivatives have to be mixed with the density matrix.4Evaluation of integralsIn this section we summarise the types of integral which occur.The simplest type is the overlap integral between two basis functions at two centres:Sµν R k R l= φµ( r− R k)φν( r− R l)d3r(4) Obviously we can shift R k to the origin,and suppressing 0in the notation,we obtain:Sµν R i= φµ( r)φν( r− R i)d3r(5) with R i= R l− R k.A kinetic energy integral has the form:Tµν R i= φµ( r)(−12∆ r)φν( r− R i)d3r(6) the nuclear attraction integral has the form:Nµν R i= φµ( r)Z c| r− A c|φν( r− R i)d3r(7) and the electron-electron interaction has the form:Bµν R iτσ R j = φµ( r)φν( r− R i)φτ( r′)φσ( r′− R j)| r− r′|d3rd3r′(8)These integrals are in principle sufficient to deal with molecules.In the case of periodic systems,new types of integrals appear(e.g.multipolar integrals,integrals over the Ewald potential and its derivatives)[11,13,14].The fast evaluation of integrals is one of the main issues in the development of quan-tum chemistry codes.CRYSTAL uses a McMurchie-Davidson algorithm[15].Its idea is to map a product of two Gaussian type orbitals at two centres in an expan-sion of Hermite polynomials at an intermediate centre.This algorithm has proven to efficiently evaluate integrals,although in recent years progress in this specialised field of quantum chemistry has been made(see for example the introduction in[16] or two recent reviews[17,18]).The expansion[15,14]looks like:5φ(α, r− A,n,l,m)φ(β, r− B,n′,l′,m′)= t,u,v E(n,l,m,n′,l′,m′,t,u,v)Λ(γ, r− P,t,u,v)(9)withγ=α+βand P=α A+β Bα+β.Λis a so-called Hermite Gaussian type function Λ(γ, r− P,t,u,v)= ∂∂P x t ∂∂P y u ∂∂P z v exp(−γ( r− P)2)(10)The start value E(0,0,0,0,0,0,0,0,0)=exp(−αβ( B− A)2)can be verified by inserting it in equation9.It can be derived from the Gaussian product rule[19,20]:exp(−α( r− A)2)exp(−β( r− B)2)=exp −αβα+β( B− A)2 exp −(α+β) r−α A+β Bα+β 2(11) General values E(n,l,m,n′,l′,m′,t,u,v)are obtained from recursion relations[15, 14].The E-coefficients depend on the distance( B− A),but not on P or r.All the integrals can be expressed in terms of E-coefficients[15,14,11,13].Evaluation of gradients of the integralsOne of the issues of the gradient project is to generalise the algorithms used to generate the energy integrals to obtain the gradients of the integrals.This madea new implementation of recursion relations necessary which are used to obtainthe coefficients G in the expansion of the gradients of the integrals in Hermite polynomials.∂Φ(α, r− A,n,l,m)Φ(β, r− B,n′,l′,m′)∂A x= t,u,v G A x(n,l,m,n′,l′,m′,t,u,v)Λ(γ, r− P,t,u,v)(12)Once the coefficients are known,the integration can be performed.The integrationfor the case of gradients of integrals is similar to the case of integrals for the total energy.The only difference is that,instead of the coefficientsE(n,l,m,n′,l′,m′,t,u,v)which enter the energy expression,the gradient coefficientsG A x(n,l,m,n′,l′,m′,t,u,v),G A y,G A z,G B x,G B y,and G B z6are used.The coefficients G B x can efficiently be obtained together with the coeffi-cients G A x[21].For example,the evaluation of the overlap integral is done as follows:Sµν R i = φµ( r)φν( r− R i)d3r=t,u,v E(n,l,m,n′,l′,m′,t,u,v)Λ(γ, r− P,t,u,v)d3r=E(n,l,m,n′,l′,m′,0,0,0)Λ(γ, r− P,0,0,0)d3r=ME(n,l,m,n′,l′,m′,0,0,0)From thefirst line to the second,we have used the McMurchie-Davidson scheme, from the second to the third we exploited a property of the Hermite Gaussian type functions:all the integrals of the type Λ(γ, r− P,t,u,v)d3r with t=0or u=0or v=0vanish because of the orthogonality of these functions.The integration(fromthe third to the fourth line)is trivial.M is a normalisation constant. Calculating the gradient is easy once we know the new expansion:∂Sµν R i ∂A x =∂∂A xφµ( r)φν( r− R i)d3r=∂ t,u,v E(n,l,m,n′,l′,m′,t,u,v)Λ(γ, r− P,t,u,v)∂A x d3r=t,u,v G A x(n,l,m,n′,l′,m′,t,u,v)Λ(γ, r− P,t,u,v)d3r=G A x(n,l,m,n′,l′,m′,0,0,0)Λ(γ, r− P,0,0,0)d3r=MG A x(n,l,m,n′,l′,m′,0,0,0)This way,all the derivatives can be calculated!There are some integrals which involve three centres(for example nuclear attraction)where we exploit translational invariance:∂∂C x =−∂∂A x−∂∂B x(13)because the value of the integral is invariant to a simultaneous uniform translation of the three centres.Four centre integrals can be reduced to a product of two integrals over two centres which makes the calculation of gradients straightforward.As a whole,the calculation of gradients of the integrals is closely related to calcu-lating the integrals itself.This means that most of the subroutines can be used for7the gradient code.One of the main differences is that array dimensions need to be changed-dealing with gradients is similar to increasing the quantum number(a derivative of an s-function is a p-function,and so on).However,the task of adjusting the subroutines should not be underestimated.After obtaining the derivatives of the integrals,we mix them with the density ma-trix just like in the energy calculation.We have to take into account the new term which arose because we did not calculate a density matrix derivative—the energy weighted density matrix.Again,coding this additional term can be done by modi-fying existing subroutines.After this,wefinally obtain the forces on the individual atoms.Results from test calculationsIn this section,we summarise results from test calculations.We have considered the CO molecule which was arranged as a single molecule,as a molecule which is peri-odically reproduced with a periodicity of4˚A in one spatial direction(”polymer”), periodically reproduced with a periodicity of4˚A in two spatial directions(”slab”), and periodically reproduced with a periodicity of4˚A in three spatial directions (”solid”).Because of the large distance of4˚A,the molecules can be considered as nearly independent and the forces are quite similar.Still,the calculation of energy and gradient is completely different and therefore this is an important test of Ewald technique and multipolar expansion.The results are given in table1.The results agree in the best case to at least6digits which is the numerical noise and in the worst case up to4digits.The difference between analytic and numerical gradi-ents in periodic systems mainly originates from an approximation made within the evaluation of the integrals[22]and from the number of k-points which affects the accuracy of the energy-weighted density matrix.In table2,we display results from a MgO solid with one oxygen atom slightly distorted from the symmetrical position.Again,the forces agree well up to5digits with numerical derivatives.Future developments and ConclusionThe present version of the code is able to calculate Hartree-Fock forces for periodic systems up to a precision of4and more digits.There is no extra diskspace needed and the additional memory usage is moderate.This code will certainly be useful for structural optimisation and for future program development towards molecular dynamics or the calculation of response functions.The present version,however,is not yet ready for a release.Instead,the following steps are necessary:Firstly,the usage of symmetry must be implemented.This is of highest importance to make the code fast enough so that it can be used for practical optimisations.We expect8Table1:Force on a CO molecule with a carbon atom located at(0˚A,0˚A,0˚A)and an oxygen atom located at(0.8˚A,0.5˚A,0.4˚A).In the periodic case,the molecule is generated with a periodicity of4˚A.This means,that in one dimension,for example,there would be other molecules with a carbon atom at(n×4˚A,0˚A,0˚A)and an oxygen atom at((n×4+0.8)˚A,0.5˚A,0.4˚A),with n running overall positive and negative integers.Forces are given in E h,with E h=27.2114eVand a0=0.529177˚A.Higher ITOLs means a lower level of approximation in the evaluation of the integrals[22].ITOLs) k-points) numerical force0.3769140.37660(0.37664)0.376310.37566(0.37566) analytical force0.3769130.37663(0.37665)0.376330.37588(0.37578))on the atoms of an MgO solid.The MgO solid was chosen Table2:Forces(in E ha0to have an artificially high lattice constant of6.21˚A to make the calculation faster. Coordinates are given in fractional units,e.g.the second Mg is at0˚A,0.5×6.21˚A,0.5×6.21˚A.A normal fcc lattice would be obtained if the sixth atom(Oxygenat0.53,0,0)was at(0.5,0,0).Moving this atom from its normal position has ledto the nonvanishing forces.Mg(0.00.00.0)-0.03018-0.03019Mg(0.00.50.5)-0.00314-0.00314Mg(0.50.00.5)0.008950.00895Mg(0.50.50.0)0.008950.00895O(0.50.50.5)-0.00379-0.00379O(0.530.00.0)0.004290.00430O(0.00.50.0)0.007460.00746O(0.00.00.5)0.007460.00746that a version of the present code with symmetry will already be fast enough to compete with numerical derivatives.Further developments will be the coding of the bipolar expansion(a method to evaluate the electron-electron repulsion integrals faster),and sp-shells(s and p shells are often chosen to have the same exponentsto make the evaluation of integrals faster).Also,the newly written subroutines arenot yet optimal and they will certainly go through a technical optimisation(moreefficient coding).In later stages,the code should be made applicable to metals (there is an extra term coming from the shape of the Fermi surface[23]which is notyet coded)and to magnetic systems(unrestricted Hartree-Fock gradients).Finally, pseudopotential gradients and density functional gradients should be included. References[1]P.Pulay,Mol.Phys.17,197(1969).[2]P.Pulay,Adv.Chem.Phys.69,241(1987).[3]P.Pulay,in Applications of Electronic Structure Theory,edited by H.F.Schae-fer III,153(Plenum,New York,1977).[4]H.B.Schlegel,Adv.Chem.Phys.67,249(1987).[5]T.Helgaker and P.Jørgensen,Adv.in Quantum Chem.19,183(1988)[6]H.Teramae,T.Yamabe,C.Satoko,A.Imamura,Chem.Phys.Lett.101,149(1983).[7]C.Pisani,R.Dovesi,and C.Roetti,Hartree-Fock Ab Initio Treatment of Crys-talline Systems,edited by G.Berthier et al,Lecture Notes in Chemistry Vol.48(Springer,Berlin,1988).[8]V.R.Saunders,R.Dovesi,C.Roetti,M.Caus`a,N.M.Harrison,R.Orlando,C.M.Zicovich-Wilson crystal98User’s Manual,Theoretical Chemistry Group, University of Torino(1998).[9]K.Doll,V.R.Saunders,N.M.Harrison(in preparation)[10]V.R.Saunders,N.M.Harrison,R.Dovesi,C.Roetti,Electronic StructureTheory:From Molecules to Crystals(in preparation)[11]V.R.Saunders,C.Freyria-Fava,R.Dovesi,L.Salasco,and C.Roetti,Mol.Phys.77,629(1992).[12]S.Bratoˇz,in Calcul des fonctions d’onde mol´e culaire,Colloq.Int.C.N.R.S.82,287(1958).[13]R.Dovesi,C.Pisani,C.Roetti,and V.R.Saunders,Phys.Rev.B28,5781(1983).[14]V.R.Saunders,in Methods in Computational Molecular Physics,edited by G.H.F.Diercksen and S.Wilson,1(Reidel,Dordrecht,Netherlands,1984).[15]L.E.McMurchie and E.R.Davidson,put.Phys.26,218(1978).[16]R.Lindh,Theor.Chim.Acta85,423(1993).[17]T.Helgaker and P.R.Taylor,in Modern Electronic Structure Theory.Part II,World Scientific,Singapore,725(1995)[18]P.M.W.Gill,in Advances in Quantum Chemistry,edited by P.-O.L¨o wdin,141(Academic Press,New York,1994)[19]S.F.Boys,Proc.Roy.Soc.A200,542(1950).[20]R.McWeeny,Nature166,21(1950).[21]T.Helgaker and P.R.Taylor,Theor.Chim.Acta83,177(1992).[22]The integrals Bµν R iτσ R j =Bτσ R jµν R iwhich should have the same value,are notnecessarily evaluated within the same level of approximation—this is nearly inevitable for periodic systems,as enforcing this symmetry would require a much higher computational effort and much more data storage.The derivation of the equations for the analytic gradients,however,relies on these integrals be-ing equivalent.Therefore,the introduced asymmetry will lead to inaccuracies in the gradients.This can be controlled with the ITOL-parameters(tolerances as described in the CRYSTAL manual[8])which control the level of approx-imation.Higher ITOLs lead to a higher accuracy in the forces.However,the defaults appear to give forces with an accuracy up to4digits which should be good enough for most purposes.[23]M.Kertesz,Chem.Phys.Lett.106,443(1984).3SRRTNet-a new global networkFrascati’99-Birth of a NetworkScientific MeetingFrom the23rd to the25th September1999,a workshop on Theory and Computation for Synchrotron Radiation was held at the laboratory in Frascati just outside Rome, Italy.This was the third in an ongoing series of meetings on various aspects of synchrotron radiation,and follows meetings on Theory and Computation for Syn-chrotron Applications held at the Advanced Light Source in Berkeley in October 1997and Needs for a Photon Spectroscopy Theory Center held at the Argonne National Laboratory in August1998.This was an excellent meeting,featuring a variety of high quality scientific pre-sentations from both experimental and theoretical participants.Thefirst day was devoted to presentations concentrating on resonant x-ray processes and orbital or-dering effects,particularly in V2O5.The second day then moved on to discussions of photoemission,photoelectron diffraction and holography,and studies of high T c superconductors.This day was concluded with an excellent conference dinner which finished rather late!Thefinal day then concluded with discussions of EXAFS,and x-ray spectroscopies.The overheads used in all the presentations can be viewed on line at http://wwwsis.lnf.infn.it/talkshow/srrtnet99.htmSRRTNet DiscussionsThe Friday programme also included a two hour session devoted to the idea of forming a global network concentrating on theory for synchrotron radiation re-search based research.The session began with a talk from Michel Van Hove of the Lawrence Berkeley National Laboratory who outlined the purposes and function of the proposed network.This was then followed by presentations by John Rehr of the University of Washington who highlighted moves to extend the synchrotron radia-tion research theory network(SRRTNet)in North America,by Maurizio Benfatto of the INFN Frascati,who presented the European perspective,by Kenji Makoshi of Himeji Institute of technology who discussed the Japanese efforts and by Adrian Wander of the Daresbury Laboratory who presented CCP3as a possible model of how the network could be run.The concept of establishing a global network was received with enthusiasm from all present.OutcomeGiven the support of the meeting for the concept of global network of this sort,it was decided to extend SRRTNet into the global arena.The aims of the network are:•To provide a central repository for information of relevance to synchrotron radiation research•To develop theoretical methods pertaining to the experiments performed on synchrotron facilities•To provide state of the art and user friendly software for the analysis and interpretation of experiments•To provide training in the use of relevant software through workshops and site visits•To host visiting scientists•To hold periodic workshops for the dissemination of new results and method-ologiesThe directors of the network are Michel Van Hove and John Rehr.As afirst step in the development of the network,Daresbury has agreed to host the web pages, and theoretical groups have been contacted and ask to provide input to this central web hub of what will grow into a globe encompassing network.If you are interested in contributing to the network and missed our e-mail announcement,the invitation letter follows;Dear Colleague,You may know of the recently established Synchrotron Radiation Research Theory Network(SRRTNet).We are contacting you to invite you,and all theorists inter-ested in this topic,to actively participate in the next phase of the network. SRRTNet aims to provide theory for experiments that use synchrotron radiation,by means of a global,web-based network linking theoretical and experimental research groups.The driving philosophy is to promote interactions between theory and exper-iment for mutual benefit,by means of web-based information,workshops,exchange of theoretical methods and computer codes,as well as establishing visiting scientist programs.At the last SRRTNet workshop,conducted at Frascati near Rome in September1999, it was decided to strengthen the global character of this network by establishing a cen-tral,web-based source of information.Daresbury Laboratory is hosting this web site with Dr.Adrian Wander acting as editor.It is anticipated that all synchrotron facilities will provide direct links for their users to this web site,and consequently we expect this site to grow into an essential resource for synchrotron radiation re-searchers.An importantfirst function of the web site will be to provide information about theorists’research interests and links to relevant web pages.The network will be all the more valuable as this coverage becomes complete:it will thus allow theorists and experimentalists alike tofind the best sources of information about the various methods for solving specific scientific problems.The purpose of this message is to ask you to provide such information and links about your group.You may visit the new web site/Activity/SRRTNetand see not only an overview of the network in general,but also the beginnings of such information about specific theoretical groups.The idea is to put a list of your research topics on the SRRTNet web site,while providing links to your own web site for more detailed and up-to-date information. If you prefer,the SRRTNet site can itself host a more complete web page covering your activities.The information we wish to present(or link to)includes as many as possible of the following items:•your topics of scientific activity related to synchrotron radiation(directly or by methodology);•your computer codes,with their capabilities and availability;•your publications,such as abstracts,papers,databases and web-presentations;•how to contact you or your group.。

Early hydration and setting of Portland cement monitored by IR,SEM and Vicat techniquesRikard Ylmén,Ulf Jäglid,Britt-Marie Steenari,Itai Panas ⁎Department of Chemistry and Biotechnology,Environmental Inorganic Chemistry,Chalmers University of Technology,S-41296Gothenburg,Swedena b s t r a c ta r t i c l e i n f o Article history:Received 26November 2007Accepted 30January 2009Keywords:HydrationCalcium-silicate-hydrate (C-S-H)Spectroscopy Cement paste Portland cementDiffuse Re flectance Infrared DR-FTIR spectroscopy is employed to monitor chemical transformations in pastes of Portland limestone cement.To obtain a suf ficient time resolution a freeze-dry procedure is used to instantaneously ceasing the hydration process.Rapid re-crystallization of sulphates is observed during the first 15s,and appears to be complete after ~30min.After ~60min,spectroscopic signatures of polymerizing silica start to emerge.A hump at 970–1100cm −1in conjunction with increasing intensity in the water bending mode region at 1500–1700cm −1is indicative of the formation of Calcium Silicate Hydrate,C-S-H.Simultaneously with the development of the C-S-H signatures,a dip feature develops at 800–970cm −1,re flecting the dissolution of Alite,C 3S.Setting times,180(initial)and 240(final)minutes,are determined by the Vicat bining DR-FTIR,SEM and Vicat measurements it is concluded that the setting is caused by inter-particle coalescence of C-S-H.©2009Elsevier Ltd.All rights reserved.1.IntroductionToday,Portland cement is a widely used binder in concrete construction.C 3S (alite)and C 2S (belite)is essential to the build-up of strength in Portland cement.These two calcium-silicate phases are formed above 800°C,where C 3S is preferentially formed upon elevating the temperature and increasing amount of added burned lime,CaO.C 3S is responsible for short term strength development (days to months)while C 2S displays the better long term strength development performances (~years).The quest for increasingly shorter setting time and early strength has seen the C 3S/C 2S ratio increase in commercial Portland cement.In recent years,the increased attention on environmental aspects of material conversion has in fluenced research towards possible modi fications of Portland cement to better meet the increasing demands for sustainability in the construction sector.This is done by using additives and changing the composition of the cement.Many different experimental techniques have been employed to investigate the effects on material conversion as Portland cement is dissolved and transformed into calcium-silicate-hydrate,C-S-H.For determination of setting times,Vicat measurements are often employed.At later stages in the hydration process,an ultrasonic cement analyser may be used to determine changes in the elastic modulus of the mortar [1,2].Calorimetry is employed to monitor the heat released upon hydration [3–7],whereas X-ray diffraction [8–13],nuclear magnetic resonance [14–16]and Fourier transform infrared spectroscopy,FTIR,are used toobtain chemical information.Morphological information may be obtained by means of scanning electron microscopy and transmission electron microscopy [11,12,15,17].Spectroscopic methods are commonly used to study the chemistry of cement hydration.In the present work the hydration of Portland cement has been monitored mainly by means of infrared spectroscopy.In infrared spectroscopy one utilizes that molecules or groups of atoms on large molecules absorbs different wavelengths of infrared light depend-ing on which atoms that constitute the molecule or group,its geometry and its immediate surroundings.It can therefore be used to study both crystalline and amorphous samples.The sample is irradiated with infrared light with a span of different wavelengths.The sample will absorb some of the light at wavelengths that are characteristic to its chemical composition.To see at which wavelengths the sample has absorbed light the intensity at each wavelength is measured with and without sample.IR radiation only penetrates about 1wavelength into the sample (~10µm for 1000cm −1),making it ideal in the study of surface processes.In previous studies where FTIR was used to study the hydration of cement and its components,the sample was prepared by mixing the cement with KBr and pressing the mixture into pellets [18–21].The usefulness of Diffuse Re flectance Fourier Transform Infrared Spectro-scopy,DR-FTIR,as a tool for studying the hydration of cement has also been demonstrated in previous work [22,23].A comparison between DR-FTIR and the KBr pellet technique has been done by Delgado et al.[24],who showed that the methods produce similar spectra.The advantage of the KBr technique is that it provides better de fined bands than DR-FTIR,but the sample preparation is more labour intensive.The results of the present study suggest that the DR-FTIR technique employed is indeedCement and Concrete Research 39(2009)433–439⁎Corresponding author.Tel.:+46317722860;fax:+46317722853.E-mail address:itai@chalmers.se (I.Panas).0008-8846/$–see front matter ©2009Elsevier Ltd.All rights reserved.doi:10.1016/j.cemconres.2009.01.017Contents lists available at ScienceDirectCement and Concrete Researchj ou r n a l h o m e pa g e :ht t p ://e e s.e l s e v i e r.c o m /C E MC ON /d e f a ul t.a s ppreferred in that external physico-chemical interference is minimized,i.e.the hydration products are studied in the proper cement matrix with a minimum of sample tampering,and avoiding contact with foreign chemicals.Differential IR light absorption of samples which have been allowed to hydrate for different times is reported here.Water displays strong absorption in the mid-IR range,which makes it virtually impossible to perform in situ studies of cement hydration.A second draw back of in situ DR-FTIR for the study of cement hydration is that the surface of the cement paste,while hydrating,may become too flat for the diffuse re flectance technique to be ef ficiently used.These considerations validate selection of an ex situ DR-FTIR approach.To study very early hydration using an ex situ technique,it is imperative that the hydration is stopped instantaneously at a predetermined time.To satisfy this requirement,a freeze-dry technique is adopted in this research.The freezing of the sample with liquid nitrogen ensures that all chemical processes are very much retarded,while the subsequent water evaporation step at low temperature minimizes any thermally induced chemical transforma-tions other than water removal while drying.Indeed,earlier microscopy work [25–27]has shown that freezing is a relatively mild method to stop hydration.The drying will of course affect the structures of some phases.Bound water,like in ettringite,could be partially removed,and morphological properties may change upon removal of water.The purpose of the present study is to demonstrate the ef ficiency of the freeze-dry procedure in conjunction with DR-FTIR spectroscopy for studying the complex hydration chemistry of Portland cement.An attempt to correlate relevant spectroscopic signatures to the devel-opment of strength in the system is also made.Strength development is monitored here by means of Vicat measurements.2.ExperimentalThe Portland cement used was a Portland limestone cement,“byggcement Std PK Skövde CEM II/A-LL 42,5R ”,from Cementa AB.An automatic/manual mortar mixer 39-0031from ELE International was used.The cement was mixed with distilled deionized water that was poured into the mixing bowl before adding the cement.The ratio of water to as received dry cement was 0.4by weight in both DR-FTIR and Vicat measurements.The cement was carefully added and the paste was mixed at 140rpm on the mixing blade and 62rpm on the mixing head.The hydration time was measured from the instant when the cement was added to the water.2.1.DR-FTIRThe spectrometer used was a Nicolet Magna-IR 560with an insert cell for diffuse re flectance spectroscopy.The measurement range liesbetween 400and 4000cm −1.The diffuse re flectance technique is utilized,in which the incident beam is allowed to be re flected off the ground sample towards an overhead mirror upon which the diffusely scattered rays are collected and measured in the detector.A more detailed description is given by Fuller and Grif fiths [28].The sample is scanned 64times with a resolution of 2.0cm −1and the presented data is an average value.Each sample was prepared and analyzed 3times and the final spectrum was an average of these 3measurements to minimize differences due to sample preparation.The batch size was 200g of as received dry cement.As the cement hydration was studied from 15s the cement paste was only mixed for 15s.However,the chemical development of the cement paste was found to be insensitive of mixing time as long as the cement was completely wetted [29].Samples were prepared in plastic dishes of 35mm in diameter.The thickness of the paste in the dishes was ~2–3mm.Lids were placed over the dishes while they hydrated to prevent water from evaporating.The samples were hydrated between 15s and 360min in normal laboratory environment,then frozen by immersion in liquid nitrogen and subsequently placed in the freeze drier overnight.Measurements were made the following day.Before measurement the sample was ground and placed in the sample holder of the DR-FTIR spectrometer.To obtain good reproducibility,great care was taken when grinding the samples and placing them in the sample cup to make the samples as similar as possible.2.2.VicatThe batch size was 300g of as received dry cement and the cement paste was mixed for 2⁎90s with a stop in between for 15s to scrape the paste from the inside walls.The Vicat apparatus used was a Vicatronic automatic recording apparatus E040and measurements were performed in a 40mm mould with a calibrated weight of 300g and a cylindrical needle with flat tip area of 1mm 2.2.3.Scanning electron microscopyThe microscope used was a FEI Quanta 200FEG ESEM operated in secondary electron detection mode with high-vacuum and an acceleration voltage of 2kV.Some of the freeze-dried samples were pulverized.Since the freeze-dried samples were barely holding together this was easily done with a metal spoon.Some of the powder was placed on carbon tape attached to the sampleholder.Fig.1.Vicat measurement showing the depth of penetration of the Vicat needle into the cement as function of time.The height of the mould was 40mm.Table 1Possible assignment to some of the peaks observed in Figs.2–5.Wave number [cm −1]Possible assignment Reference656–658υ4of SiO 4[21,40]714υ4of CO 3[22,32,35,37]847–848Al –O,Al –OH [21,35]877–878υ2of CO 3[21,22,35,37]1011–1080Polymerized silica [19]~1100–1200υ3of SO 4[19,22,31,32]1200–1202Syngenite,thenardite [32–34]1400–1500CO 3[19,21,22,35,37]1620–1624υ2of water in sulphates [22,31,33]1640–1650υ2H 2O[21,35,36]1682–1684υ2of water in sulphates [22,31,33]1795–1796CaCO 3Own measurement,[22]2513–2514CaCO 3Own measurement,[22]2875–2879CaCO 3Own measurement,[22]2983–2984CaCO 3Own measurement,[22]3319–3327Syngenite,thenardite [32–34]3398–3408υ3of H 2O,capillary water [36]3457υ1+υ3of H 2O[21,36]3554υ3of H 2O in gypsum [22,31]3611Bassanite [22]3641–3644Ca(OH)2Own measurement,[20,23,24,37]434R.Ylmén et al./Cement and Concrete Research 39(2009)433–439Several regions were examined to make sure that the observed structures were representative of the sample.3.ResultsThe present study attempts to correlate setting with the evolution of spectral features in DR-FTIR spectra during early hydration of cement.The Vicat setting time measurement for the used Portland cement is displayed in Fig.1.Initial andfinal set are seen to occur at 180min and240min respectively.In Section3.1,the overall time evolution of DR-FTIR absorption intensities is presented.Possible assignments of the different bands are shown in Table1,and interpreted in Sections3.1.2–3.1.4.3.1.Time resolved spectra of hydrating cementThe hydration process was monitored for thefirst six hours by applying the freeze dry method,grinding of sample and subsequently acquiring the DR-FTIR spectra.The recorded absolute spectra of dry and hydrated cement are displayed in Fig.2.It shows the spectra of theas received dry cement together with the cement just after it has been mixed(15s),after180min and360min of hydration.Weak signatures of hydration can be seen in the900–1200cm−1region.To enhance these effects,various difference spectra were constructed.In Fig.3,the difference spectra employ as received dry cement as reference.Now, the spectroscopic features can be seen significantly clearer and we observe the development and saturation band at1100–1200cm−1 already after15s.This is complemented by a more slowly growing feature at900–1100cm−1.Because the bands that developed after 15s cannot be associated with the actual hardening of cement paste, the15s spectrum was taken as reference in Figs.4and5.Fig.3 supports the overall procedure in that a smooth background is observed in the relevant spectral regions.Having found this,Fig.5 focuses on the500–2000cm−1interval and the spectra for twelve different hydration times are displayed.3.1.1.Sulphate bandsThe sulphates originally present in Portland cement are gypsum (CaSO4·2H2O),hemihydrate(bassanite,CaSO4·0.5H2O)and anhy-drite(CaSO4).The latter ones are formed when the gypsum is ground with the cement clinker.The heat makes some of the crystal water in the gypsum to dissociate.When water is added to the cement the sulphates react with the aluminate and ferrite phases of the cement to produce AFt phase.This phase in turn reacts further with the aluminate and ferrite phases to form the AFm phase[30].Characteristic sulphate absorption bands are generally found in the range1100–1200cm−1due to theυ3vibration of the SO42−-group in sulphates[19,22,31,32].It is very difficult to interpret this area by studying FTIR-spectra only,since the many forms of sulphates give rise to several peaks here and cause lots of overlaps,but also because the υ3vibration of the SiO42−-group can absorb in this region,especially when it has polymerized[21].Therefore no in-depth analysis of it will be done in this work.In the DR-FTIR spectrum of as received dry cement(Fig.2,bottom spectrum),a broad feature is seen in1100–1200cm−1region reflecting mainly amorphous sulphates.Immedi-ately after mixing with water,some sharp absorption bands develop at 1100cm−1,1200cm−1and3320cm−1,indicative of very rapid dissolution of sulphates followed by crystallization(Fig.2,15s spectrum).This can also be inferred by considering the15s difference spectrum in Fig.3.This spectrum corresponds to the difference between that acquired after15s of hydration,and the spectrum of dry cement.Spectral signatures of sulphate chemistry after15s of hydration,corresponding to re-crystallization are obtained.Appar-ently,crystalline sulphate phases form very early in the hydration process,after which they become inactive spectator phases.The extent to which this holds true can be assessed by replacing the as received dry cement reference spectrum for that of15s hydrated cement(Figs.4and5).From Fig.5we observe significant changes in the sulphate absorption bands up to30min of hydration.Apparently, intermediate phases are formed consistent with theabsorptionFig.2.Absorbance of as received dry cement and cement that has been allowed tohydrate for15s,180min and360min after the cement was added to the water.Thespectra are shown offset forclarity.Fig.3.Difference spectra where the absorbance spectrum of as received dry cement hasbeen subtracted from the absorbance spectra of cement hydrated for15s,180min and360min.The spectra are shown offset forclarity.Fig.4.Difference spectra in the range400–4000cm−1where the absorbance spectrumof the freshly mixed cement(15s)has been subtracted from the absorbance spectra ofcement hydrated for30s,5min,120min and360min.The spectra are shown offset forclarity.435R.Ylmén et al./Cement and Concrete Research39(2009)433–439spectra of syngenite (K 2Ca(SO 4)2·H 2O)and thenardite (Na 2SO 4)or closely related compounds [32–34].At any rate,after 60min,little changes can be seen in the sulphate absorption region of the spectra.3.1.2.Water associated bandsIn the spectrum for as received dry cement there is a peak at 1623cm −1and a smaller one at 1684cm −1.These are caused by the bending vibration υ2of water in sulphates,mainly gypsum [22,31,33].The peak at 3554cm −1is caused by the υ3vibration of water in gypsum [22,31]and the peak at 3611cm −1could be caused by bassanite (CaSO 4·0.5H 2O).As hydration progresses there is a broad feature forming with its centre at ~1650cm −1,caused by the bending vibration υ2of irregularly bound water [21,35,36].The consumption of gypsum can be seen as dips in this feature at 1623cm −1and 1680cm −1(Figs.4and 5).A small increase in gypsum during the first 10min is implied,and may be due to the transformations of anhydrite and bassanite.The “background ”level for wave numbers N 1600cm −1is steadily increasing with increasing hydration times.Since there seems to be no corresponding decrease in any other area,this is probably caused by the incorporation of water.The absorption intensities due to the υ2vibration mode of water at ~1650cm −1and the υ1+υ3modes at ~3450cm −1and results from Mollah et al.and Yu et al.support this observation [21,36].3.1.3.Silica associated bandsAfter about 2h of hydration new spectral intensity shifts are observed from ~900cm −1towards ~1000–1100cm −1(see Figs.3–5),neither associated with sulphates nor water,suggestive of rearrange-ments in the silica subsystem.These dip-hump features are taken to re flect dissolution of alite and simultaneously the polymerization ofsilica [21,23,37,38]to form calcium silicate hydrate C-S-H (vide infra ).In order to focus on the silica chemistry,the 15s reference spectrum is replaced by that acquired after 30min (see Fig.6),i.e.after the sulphate chemistry has stopped.Monotonous growth of the C-S-H associated absorption intensities (970–1100cm −1)is observed.The dip in the absorption spectrum at 800–970cm −1,which deepens with time,is due to the dissolution of the C 3S clinker phase [39].The intensities in the dip (800–970cm −1)and hump (970–1100cm −1)regions in Fig.6were integrated in an attempt to correlate the clinker dissolution with the silica polymerization.A horizontal line at the intensity at 970cm −1was used as baseline.The result is plotted in Fig.7.3.1.4.Hydroxides and carbonatesThe peak at 3643cm −1(see Table 1and Figs.2and 3)corresponds to Ca(OH)2,which is formed as silicate phases in the cement dissolve.The peaks at 1796cm −1,2513cm −1,2875cm −1,2983cm −1and the shoulder at 1350–1550cm −1are due to that portion of calcium carbonate,which is added to the cement by the manufacturer after clinker calcination.The amount of calcium carbonate is seen to decrease as the hydration progresses,i.e.negative absorption bands in the difference spectra of Figs.3and 4.This may partly be due to the reaction of calcite with the aluminate to form less crystalline phases such as carboxyaluminates [40,41]or the carbonate ion can substitute for sulphate ions in Aft and AFm phases [13,30].The peak growing at ~1070cm −1could be the υ1vibration of CO 3-group in the formed carbonates [33,35],but this observation would contradict theoverallFig.6.Difference spectra in the range 500–2000cm −1where the absorbance spectrum of cement hydrated for 30min has been subtracted from the absorbance spectra of cement with hydration times from 60–360min.The spectra are shown offset forclarity.Fig.7.Integrated value of the absorbance in the intervals 800–970cm −1(upper dots)and 970–1100cm −1(lower dots)in Fig.6as function of hydration time of the cement.The lines are drawn on free hand to guide the eye and does not represent a mathematicalmodel.Fig.5.Difference spectra in the range 500–2000cm −1where the absorbance spectrum of the freshly mixed cement (15s)has been subtracted from the absorbance spectra of cement with hydration times from 30s to 360min.The spectra are shown offset for clarity.436R.Ylmén et al./Cement and Concrete Research 39(2009)433–439Fig.8.SEM pictures of cement at different stages of hydration.a)Surface of unhydrated particle.b)Surface of particle hydrated for 15s.c)Surface of particle hydrated for 120min.d)Surface of particle hydrated for 240min.e)Surface of particle hydrated for 480min.f)Surface of particle hydrated for 480min at larger magni fication.437R.Ylmén et al./Cement and Concrete Research 39(2009)433–439reduction of carbonate absorption intensities with time.A more plausible candidate for this absorption band is the stretching vibration of Si–O,which is also found in jennite(Ca8(Si6O18H2)(OH)8Ca·6H2O) [37,38].3.2.SEMSEM pictures of cement grains at different stages of hydration are displayed in Fig.8.The surfaces of the unhydrated particles are bare, with debris lying on top(Fig.8a).After15s and120min of hydration (Fig.8b,c)the surfaces of the cement particles are still found to be bare,but lumps and platelets have formed in addition to the debris present already on the unhydrated particles.Fig.8d shows cement after240min of hydration.Now a carpet is covering the cement particles.The carpet has grown even more after480min of hydration and is seen to consist of needle-like protruding structures(Fig.8e,f).4.DiscussionA longstanding issue concerns the roles of various phases during early hardening of Portland cement.In particular the roles of sulphates,added to the Portland cement as anhydrous(CaSO4), hemihydrate(CaSO4·0.5H2O),and gypsum(CaSO4·2H2O)have been much discussed in this context.Indeed,the general consensus is that the dissolution and re-crystallization of the various sulphate contain-ing phases is completed well before the setting occurs[42,43].Yet,due to the complexity and instability of the early cement chemistry,the sulphates,besides their well known function as water absorbents, have been empirically found to affect the morphology of the hydrating paste both by providing a background ionic strength and by forming intermediate phases,which suppress“flash setting”.In the present study,results show that the sulphate related DR-FTIR absorption bands display large changes in the1100–1200cm−1interval but that this occurs mainly during thefirst10min of hydration,during which the development of sharp bands imply the formation of crystalline phases.The appearing platelets and hexagonal crystals seen with SEM are possibly associated with these phases.After30min,the inter-conversion of sulphate phases has apparently stopped.The sulphates formed are most probably ettringite or monosulphate,as earlier studies on cement hydration have shown that these sulphates are formed during thefirst minutes of hydration[11,43,44].In this study of the evolution of the C-S-H absorption bands,the30min spectrum was chosen as reference.The degree to which the sulphate chemistry is completed at this time can be appreciated by studying1100–1200cm−1region in Fig.6,keeping in mind that C-S-H also displays absorption bands in this interval.By DR-FTIR spectroscopy,detectable amounts of polymerized silica are formed after approximately1h of hydration,as seen in Fig.6in the 900–1100cm−1interval.It is gratifying to note how well the integrated intensities at800–970cm−1as function of time(Fig.7) correlate with the quantitative X-ray diffraction study on C3S hydration by Taylor et al.[45],who interpreted their results to imply C-S-H formation.The fact that the growth of the hump feature at970–1100cm−1follows the C3S dissolution process implies that the signature of polymeric silica indeed corresponds to C-S-H formation.It can be noted how the formation of polymerized silica(970–1100cm−1) is correlated in time with an increased incorporation of water in the structure as seen in the absorption interval at1500–1700cm−1.This supports further that calcium silica hydrate C-S-H is a major product formed upon early Portland cement hydration,as C-S-H consists of polymerized silica and calcium ions with water incorporated.It becomes interesting to attempt to correlate the materials conversion observed with DR-FTIR with morphological changes as seen with SEM.The acceleration phase of C-S-H formation starts somewhere between120and180min(Figs.6and7).Simulta-neously a growth of a needle-like phase is developed on the cement particles(Fig.8).This phase has been attributed to C-S-H in previous studies of alite,C3S,where no other phase than C-S-H and portlandite(Ca(OH)2)is formed[25,46].It is seen in Fig.1that the setting starts after180min,and that it is completed after240min. Since the conversion of the sulphates occurs during thefirst30min, the possibility that the needle-like phase is due to sulphates is ruled out.However,the acceleration phase of C-S-H formation(vide supra) occurs on the same time scale as the formation of the needle-like phase seen by SEM as well as that of the setting process.An identification of C-S-H as the phase responsible for the setting of the Portland cement is thus arrived at.Support is produced to the claim that C-S-H is responsible for the initial development of strength in Portland cement pastes.Also,it is suggested that C-S-H is formed continuously during hydration and in particular so prior to the setting.This implies that the actual setting is due to coalescence of clinker grains and that it is associated with the formation of sufficient amounts of C-S-H,to increase friction and bridge the inter-grain distances.The presentfindings are consistent with those of Chen and Odler [43],who reach the conclusion that setting in ordinary Portland cement is mainly due to the formation of C-S-H as long as the ratio between sulphates and C3A+C4AF is balanced,else“false setting”results due to the formation of ettringite or monosulphate.5.ConclusionsCement is a complex material,and its hydration possibly provides additional complexity.Indeed,as yet no single method exists which completely determines all chemical reactions taking place in a cement structure from the mixing and onward.Therefore several comple-mentary techniques must be used.In the present study,signatures of early setting of an untampered limestone Portland cement were extracted by correlating DR-FTIR,SEM, and Vicat measurements.The objective of this paper was to demonstrate how diffuse reflectance Fourier transform infrared spectroscopy in combination with freeze-drying may add a piece of the puzzle regarding material conversion during the very early stages of cement hydration, down to fractions of a minute.Whereas setting of each unique cement must be addressed separately,a method to monitor the material conversions during early hydration has been presented.Summarizing:•the time evolution of the sulphate chemistry displays very rapid crystallization followed by a slow recrystallization phase,which is completed within approximately30min;•the appearance of a broad absorption hump at970–1100cm−1after 60min of hydration is due to polymeric silica.It is correlated with the development of water bending vibration bands(1500–1700cm−1). This implies the formation of calcium silicate hydrate,C-S-H;•time dependent changes in morphology due to the hydration process,as monitored with SEM,were found to correlate with the DR-FTIR signatures of C-S-H formation,•the growth of a dip feature in the spectra at800–970cm−1,identified as the dissolution of C3S Alite,correlates with the formation of C-S-H.Vicat setting begins after180min and is completed after240min. This occurs well after the sulphate reactions have stopped.However, the C-S-H formation in the acceleration phase of C3S dissolution, displays the same time dependence as that of the setting process.The observations support the understanding of setting in terms of coalescing C-S-H coated Portland cement particles.AcknowledgementsThe support from the Knowledge foundation(KK stiftelsen),the Swedish Research Council,and Eka Chemicals Inc.,Bohus is gratefully acknowledged,as well as valuable discussions with Inger Jansson.438R.Ylmén et al./Cement and Concrete Research39(2009)433–439。

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A BibliographyCIE 140-2000 Road Lighting Calculations - Revision 2: December 2006CIE 141-2001 Testing of Supplementary Systems of PhotometryCIE 142-2001 Improvement to Industrial Colour-Difference EvaluationCIE 143-2001 International Recommendations for Colour Vision Requirements for TransportCIE 144-2001 ROAD SURFACE AND ROAD MARKING REFLECTION CHARACTERISTICSCIE 145-2002 THE CORRELATION OF MODELS FOR VISION AND VISUAL PERFORMANCECIE 146/147-2002 CIE COLLECTION on GLARE 2002CIE 148-2002 ACTION SPECTROSCOPY OF SKIN WITH TUNABLE LASERSCIE 149-2002 THE USE OF TUNGSTEN FILAMENT LAMPS AS SECONDARY STANDARD SOURCESCIE 150-2003 GUIDE ON THE LIMITATION OF THE EFFECTS OF OBTRUSIVE LIGHT FROM OUTDOOR LIGHTING INSTALLATIONSCIE 151-2003 SPECTRAL WEIGHTING OF SOLAR ULTRA VIOLET RADIATIONCIE 153-2003 REPORT ON AN INTERCOMPARISON OF MEASUREMENTS OF THE LUMINOUS FLUX OF HIGHPRESSURE SODIUM LAMPS - (A)CIE 154-2003 THE MAINTENANCE OF OUTDOOR LIGHTING SYSTEMS - (C)CIE 155-2003 ULTRA VIOLET AIR DISINFECTION - (G)CIE 156-2004 GUIDELINES FOR THE EV ALUATION OF GAMUT MAPPING ALGORITHMS - (C)CIE 157-2004 CONTROL OF DAMAGE TO MUSEUM OBJECTS BY OPTICAL RADIATION - (D)CIE 158-2004 OCULAR LIGHTING EFFECTS ON HUMAN PHYSIOLOGY AND BEHA VIOUR - (F)CIE 159-2004 A COLOUR APPEARANCE MODEL FOR COLOUR MANAGEMENT SYSTEMS: CIECAM02 - (C)CIE 160-2004 A REVIEW OF CHROMATIC ADAPTATION TRANSFORMS - (D)CIE 161-2004 LIGHTING DESIGN METHODS FOR OBSTRUCTED INTERIORSCIE 162-2004 CHROMATIC ADAPTATION UNDER MIXED ILLUMINATION CONDITION WHEN COMPARING SOFTCOPY AND HARDCOPY IMAGES - (C)CIE 163-2004 THE EFFECTS OF FLUORESCENCE IN THE CHARACTERIZATION OF IMAGING MEDIA - (B)CIE 164-2005 HOLLOW LIGHT GUIDE TECHNOLOGY AND APPLICATIONSCIE 165-2005 CIE 10 DEGREE PHOTOPIC PHOTOMETRIC OBSERVERCIE 167-2005 RECOMMENDED PRACTICE FOR TABULATING SPECTRAL DATA FOR USE IN COLOUR COMPUTATIONSCIE 168-2005 CRITERIA FOR THE EV ALUATION OF EXTENDED-GAMUT COLOUR ENCODINGSCIE 169-2005 PRACTICAL DESIGN GUIDELINES FOR THE LIGHTING OF SPORT EVENTS FOR COLOUR TELEVISION AND FILMING CIE 170-1-2006 FUNDAMENTAL CHROMATICITY DIAGRAM WITH PHYSIOLOGICAL AXES 鈥?PART 1CIE 171-2006 TEST CASES TO ASSESS THE ACCURACY OF LIGHTING COMPUTER PROGRAMSCIE 172-2006 UV PROTECTION AND CLOTHINGCIE 173-2006 TUBULAR DAYLIGHT GUIDANCE SYSTEMSCIE 174-2006 ACTION SPECTRUM FOR THE PRODUCTION OF PREVITAMIN D3 IN HUMAN SKINCIE 175-2006 A FRAMEWORK FOR THE MEASUREMENT OF VISUAL APPEARANCE - BilingualCIE 176-2006 GEOMETRIC TOLERANCES FOR COLOUR MEASUREMENTS - BilingualCIE 177-2007 COLOUR RENDERING OF WHITE LED LIGHT SOURCESCIE 178 VOL 1-1-2007 26TH SESSION OF THE CIE BEIJING - 4 JULY - 11 JULY 2007 PROCEEDINGS Volume 1 Part 1CIE 178 VOL 1-2-2007 26TH SESSION OF THE CIE BEIJING - 4 JULY - 11 JULY 2007 PROCEEDINGS Volume 1 Part 2CIE 178 VOL 2-2007 26TH SESSION OF THE CIE BEIJING - 4 JULY - 11 JULY 2007 PROCEEDINGS Volume 2CIE 179-2007 METHODS FOR CHARACTERISING TRISTIMULUS COLORIMETERS FOR MEASURING THE COLOUR OF LIGHT CIE 180-2007 ROAD TRANSPORT LIGHTING FOR DEVELOPING COUNTRIESCIE 181-2007 HAND PROTECTION BY DISPOSABLE GLOVES AGAINST OCCUPATIONAL UV EXPOSURECIE 182-2007 CALIBRATION METHODS AND PHOTOLUMINESCENT STANDARDS FOR TOTAL RADIANCE FACTOR MEASUREMENTSCIE 183-2008 DEFINITION OF THE CUT-OFF OF VEHICLE HEADLIGHTSCIE 184-2009 INDOOR DAYLIGHT ILLUMINANTSCIE S 004/E-2001 Colours of Light SignalsCIE S 005/E-1998 CIE Standard Illuminants for Colorimetry - ISO 10526: 1999CIE S 006.1/E-1999 Road Traffic Lights - Photometric Properties of 200 mm Roundel Signals - First Edition; ISO 16508CIE S 007/E-1998 Erythema Reference Action Spectrum and Standard Erythema Dose - ISO 17166: 1999CIE S 008/E-2001 Lighting of Indoor Work PlacesCIE S 009/E-2006 Photobiological Safety of Lamps and Lamp SystemsCIE S 010/E-2004 Photometry The CIE system of physical photometry - (E)CIE S 010/E-2004 PHOTOMETRY - THE CIE SYSTEM OF PHYSICAL PHOTOMETRY - (E)CIE S 011/E-2003 Spatial Distribution of Daylight - CIE Standard General SkyCIE S 012/E-2004 Standard method of assessing the spectral quality of daylight simulators for visual appraisal and measurement of colour - (E) CIE S 013/E-2003 International Standard Global Solar UV IndexCIE S 014-1/E-2006 Colorimetry 鈥?Part 1: CIE standard colorimetric observersCIE S 014-2/E-2006 Colorimetry - Part 2: CIE Standard IlluminantsCIE S 014-4/E-2007 Colorimetry 鈥?Part 4: CIE 1976 L*a*b* Colour spaceCIE S 015/E-2005 Lighting of Outdoor Work PlacesCIE S 019/E-2006 Photocarcinogenesis Action Spectrum (Non-Melanoma Skin Cancers) - (E)CIE S 020/E-2007 Emergency LightingCIE X005-1992 Proceedings of the CIE Seminar on Computer Programs for Light and Lighting: 5-9 October 1992 CIE Central Bureau Vienna, Austria (Table of Contents Only) (E)CIE X006-1991 Japan CIE Session at Prakash 91: Papers Presented by Japanese CIE Members in New Delhi,India, from October 7th to 13th, 1991 (Table of Contents Only) (E)CIE X007-1993 Proceedings of the CIE Symposium on Advanced Colorimetry: 8-10 June 1993 CIE Central Bureau Vienna, Austria (Table of Contents Only) (E)CIE X008-1994 Urban Sky Glow, A Worry for Astronomy: Proceedings of a Symposium of CIE TC 4-21: 3 April 1993 Royal Observatory Edinburgh, Scotland (Table of Contents Only) (E)CIE X009-1995 Proceedings of the CIE Symposium on Advances in Photometry: 1-3 December 1994 CIE Central Bureau, Vienna, Austria (Table of Contents Only) (E)CIE X010-1996 Proceedings of the CIE Expert Symposium 麓96 Colour Standards for Image Technology 25 - 27 March 1996 at the CIE Central Bureau Vienna, Austria - Table of Contents OnlyCIE X011-1996 Special Volume 23rd Session of the CIE New Delhi, November 1-8, 1995 Late Papers - Table of Contents OnlyCIE X012-1997 Proceedings of the NPL - CIE-UK Conference Visual Scales; Photometric and Colorimetric Aspects; 24 - 26 March 1997 at the National Physical Laboratory Teddington, UKCIE X013-1997 Proceedings of the CIE LED Symposium 麓97 on Standard Methods for Specifying and Measuring LED Characteristics; 24 - 25 October 1997 at the CIE Central Bureau Vienna, AustriaCIE X014-1998 Proceedings of the CIE Expert Symposium 麓97 on Colour Standards for Imaging Technology 21-22 November 1997 at the Radisson Resort Scottsdale, Arizona USACIE X015-1998 Proceedings of the First CIE Cymposium on Lighting Quality 9 - 10 May 1998 at the National Research Council Canada Ottowa, Ontario CanadaCIE X016-1998 Reference Book Based on Presentation Given by Health and Safety Experts on Optical Radiation Hazards; September 1-3, 1998; Gaithersburg, Maryland, USA (Table of Contents Only) (E)CIE X017-2000 Special Volume; 24th Session of the CIE; Warsaw, June 24 - 30, 1999; Late Papers (Table of Content Only) (E)CIE X018-1999 Proceedings of the CIE Symposium '99; 75 Years of CIE Photometry; 30 September - 02 October 1999 at the Hungarian Academy of Sciences; Budapest, Hungary (Table of Contents Only) (E)CIE X019-2001 Proceedings of Three CIE Workshops on Criteria for Road Lighting - Durban, Sourth Africa, 1997; Bath, United Kindgom, 1998; Warsaw, Poland, 1999CIE X020-2001 Proceedings of the CIE Expert Symposium 2001 on Uncertainty Evaluation Methods for Analysis of Uncertainties in Optical Radiation Measurement - 23 - 24 January 2001 at the CIE Cental Bureau; Vienna, AustriaCIE X021-2001 PROCEEDINGS of the CIE Expert Symposium 2000 on Extended Range Colour SpacesCIE X022-2001 PROCEEDINGS of the 2nd CIE Expert Symposium on LED Measurement Standard methods for specifying and measuring LED and LED cluster characteristicsCIE X023-2002 Proceedings of two CIE Worshops on Photometric Measurement Systems for Road Lighting InstallationsCIE X024-2002 PROCEEDINGS of the CIE/ARUP Symposium on Visual EnvironmentCIE X025-2002 PROCEEDINGS of the CIE Symposium '02 Temporal and Spatial Aspects of Light and Colour Perception and MeasurementCIE X026-2004 PROCEEDINGS of the CIE Symposium '04 LED Light Sources: Physical Measurement and Visual and Photobiological Assessment - Second Edition; CD-ROM INCLUDEDCIE X027-2004 PROCEEDINGS of the CIE Symposium '04 Light and Health: non-visual effects - CD-ROM INCLUDEDCIE X028-2005 PROCEEDINGS of the CIE Symposium '05 Vision and Lighting in Mesopic Conditions - CD-ROM INCLUDEDCIE X029-2006 PROCEEDINGS of the 2nd CIE Expert Symposium on Measurement UncertaintyCIE X030-2006 PROCEEDINGS of the ISCC/CIE Expert Symposium '06 75 Years of the CIE Standard Colorimetric Observer - 16 - 17 May 2006 National Research Council of Canada Ottawa, Ontario, Canada; Includes CD-ROMCIE X031-2006 PROCEEDINGS of the 2nd CIE Expert Symposium on Lighting and Health - CD-ROM INCLUDEDCIE X032-2007 Proceedings of the CIE Expert Symposium VISUAL APPEARANCE 19-20 October 2006, Paris, FranceCIE X033-2008 PROCEEDINGS of the CIE Expert Symposium on Advances in Photometry and Colorimetry 7-8 July 2008 Hotel Concorde Turin, Italy - CD-ROM INCLUDED。

2011年技术物理学院08级（激光方向）专业英语翻译重点！！！作者：邵晨宇Electromagnetic电磁的principle原则principal主要的macroscopic宏观的microscopic微观的differential微分vector矢量scalar标量permittivity介电常数photons光子oscillation振动density of states态密度dimensionality维数transverse wave横波dipole moment偶极矩diode 二极管mono-chromatic单色temporal时间的spatial空间的velocity速度wave packet波包be perpendicular to线垂直be nomal to线面垂直isotropic各向同性的anistropic各向异性的vacuum真空assumption假设semiconductor半导体nonmagnetic非磁性的considerable大量的ultraviolet紫外的diamagnetic抗磁的paramagnetic顺磁的antiparamagnetic反铁磁的ferro-magnetic铁磁的negligible可忽略的conductivity电导率intrinsic本征的inequality不等式infrared红外的weakly doped弱掺杂heavily doped重掺杂a second derivative in time对时间二阶导数vanish消失tensor张量refractive index折射率crucial主要的quantum mechanics 量子力学transition probability跃迁几率delve研究infinite无限的relevant相关的thermodynamic equilibrium热力学平衡（动态热平衡）fermions费米子bosons波色子potential barrier势垒standing wave驻波travelling wave行波degeneracy简并converge收敛diverge发散phonons声子singularity奇点（奇异值）vector potential向量式partical-wave dualism波粒二象性homogeneous均匀的elliptic椭圆的reasonable公平的合理的reflector反射器characteristic特性prerequisite必要条件quadratic二次的predominantly最重要的gaussian beams高斯光束azimuth方位角evolve推到spot size光斑尺寸radius of curvature曲率半径convention管理hyperbole双曲线hyperboloid双曲面radii半径asymptote渐近线apex顶点rigorous精确地manifestation体现表明wave diffraction波衍射aperture孔径complex beam radius复光束半径lenslike medium类透镜介质be adjacent to与之相邻confocal beam共焦光束a unity determinant单位行列式waveguide波导illustration说明induction归纳symmetric 对称的steady-state稳态be consistent with与之一致solid curves实线dashed curves虚线be identical to相同eigenvalue本征值noteworthy关注的counteract抵消reinforce加强the modal dispersion模式色散the group velocity dispersion群速度色散channel波段repetition rate重复率overlap重叠intuition直觉material dispersion材料色散information capacity信息量feed into 注入derive from由之产生semi-intuitive半直觉intermode mixing模式混合pulse duration脉宽mechanism原理dissipate损耗designate by命名为to a large extent在很大程度上etalon 标准具archetype圆形interferometer干涉计be attributed to归因于roundtrip一个往返infinite geometric progression无穷几何级数conservation of energy能量守恒free spectral range自由光谱区reflection coefficient（fraction of the intensity reflected）反射系数transmission coefficient（fraction of the intensity transmitted）透射系数optical resonator光学谐振腔unity 归一optical spectrum analyzer光谱分析grequency separations频率间隔scanning interferometer扫描干涉仪sweep移动replica复制品ambiguity不确定simultaneous同步的longitudinal laser mode纵模denominator分母finesse精细度the limiting resolution极限分辨率the width of a transmission bandpass透射带宽collimated beam线性光束noncollimated beam非线性光束transient condition瞬态情况spherical mirror 球面镜locus（loci）轨迹exponential factor指数因子radian弧度configuration不举intercept截断back and forth反复spatical mode空间模式algebra代数in practice在实际中symmetrical对称的a symmetrical conforal resonator对称共焦谐振腔criteria准则concentric同心的biperiodic lens sequence双周期透镜组序列stable solution稳态解equivalent lens等效透镜verge 边缘self-consistent自洽reference plane参考平面off-axis离轴shaded area阴影区clear area空白区perturbation扰动evolution渐变decay减弱unimodual matrix单位矩阵discrepancy相位差longitudinal mode index纵模指数resonance共振quantum electronics量子电子学phenomenon现象exploit利用spontaneous emission自发辐射initial初始的thermodynamic热力学inphase同相位的population inversion粒子数反转transparent透明的threshold阈值predominate over占主导地位的monochromaticity单色性spatical and temporal coherence时空相干性by virtue of利用directionality方向性superposition叠加pump rate泵浦速率shunt分流corona breakdown电晕击穿audacity畅通无阻versatile用途广泛的photoelectric effect光电效应quantum detector 量子探测器quantum efficiency量子效率vacuum photodiode真空光电二极管photoelectric work function光电功函数cathode阴极anode阳极formidable苛刻的恶光的irrespective无关的impinge撞击in turn依次capacitance电容photomultiplier光电信增管photoconductor光敏电阻junction photodiode结型光电二极管avalanche photodiode雪崩二极管shot noise 散粒噪声thermal noise热噪声1.In this chapter we consider Maxwell’s equations and what they reveal about the propagation of light in vacuum and in matter. We introduce the concept of photons and present their density of states.Since the density of states is a rather important property，not only for photons，we approach this quantity in a rather general way. We will use the density of states later also for other(quasi-) particles including systems of reduced dimensionality.In addition,we introduce the occupation probability of these states for various groups of particles.在本章中，我们讨论麦克斯韦方程和他们显示的有关光在真空中传播的问题。

2011年技术物理学院08级（激光方向）专业英语翻译重点！！！作者：邵晨宇Electromagnetic电磁的principle原则principal主要的macroscopic宏观的microscopic微观的differential微分vector矢量scalar标量permittivity介电常数photons光子oscillation振动density of states态密度dimensionality维数transverse wave横波dipole moment偶极矩diode 二极管mono-chromatic单色temporal时间的spatial空间的velocity速度wave packet波包be perpendicular to线垂直be nomal to线面垂直isotropic各向同性的anistropic各向异性的vacuum真空assumption假设semiconductor半导体nonmagnetic非磁性的considerable大量的ultraviolet紫外的diamagnetic抗磁的paramagnetic顺磁的antiparamagnetic反铁磁的ferro-magnetic铁磁的negligible可忽略的conductivity电导率intrinsic本征的inequality不等式infrared红外的weakly doped弱掺杂heavily doped重掺杂a second derivative in time对时间二阶导数vanish消失tensor张量refractive index折射率crucial主要的quantum mechanics 量子力学transition probability跃迁几率delve研究infinite无限的relevant相关的thermodynamic equilibrium热力学平衡（动态热平衡）fermions费米子bosons波色子potential barrier势垒standing wave驻波travelling wave行波degeneracy简并converge收敛diverge发散phonons声子singularity奇点（奇异值）vector potential向量式partical-wave dualism波粒二象性homogeneous均匀的elliptic椭圆的reasonable公平的合理的reflector反射器characteristic特性prerequisite必要条件quadratic二次的predominantly最重要的gaussian beams高斯光束azimuth方位角evolve推到spot size光斑尺寸radius of curvature曲率半径convention管理hyperbole双曲线hyperboloid双曲面radii半径asymptote渐近线apex顶点rigorous精确地manifestation体现表明wave diffraction波衍射aperture孔径complex beam radius复光束半径lenslike medium类透镜介质be adjacent to与之相邻confocal beam共焦光束a unity determinant单位行列式waveguide波导illustration说明induction归纳symmetric 对称的steady-state稳态be consistent with与之一致solid curves实线dashed curves虚线be identical to相同eigenvalue本征值noteworthy关注的counteract抵消reinforce加强the modal dispersion模式色散the group velocity dispersion群速度色散channel波段repetition rate重复率overlap重叠intuition直觉material dispersion材料色散information capacity信息量feed into 注入derive from由之产生semi-intuitive半直觉intermode mixing模式混合pulse duration脉宽mechanism原理dissipate损耗designate by命名为to a large extent在很大程度上etalon 标准具archetype圆形interferometer干涉计be attributed to归因于roundtrip一个往返infinite geometric progression无穷几何级数conservation of energy能量守恒free spectral range自由光谱区reflection coefficient（fraction of the intensity reflected）反射系数transmission coefficient（fraction of the intensity transmitted）透射系数optical resonator光学谐振腔unity 归一optical spectrum analyzer光谱分析grequency separations频率间隔scanning interferometer扫描干涉仪sweep移动replica复制品ambiguity不确定simultaneous同步的longitudinal laser mode纵模denominator分母finesse精细度the limiting resolution极限分辨率the width of a transmission bandpass透射带宽collimated beam线性光束noncollimated beam非线性光束transient condition瞬态情况spherical mirror 球面镜locus（loci）轨迹exponential factor指数因子radian弧度configuration不举intercept截断back and forth反复spatical mode空间模式algebra代数in practice在实际中symmetrical对称的a symmetrical conforal resonator对称共焦谐振腔criteria准则concentric同心的biperiodic lens sequence双周期透镜组序列stable solution稳态解equivalent lens等效透镜verge 边缘self-consistent自洽reference plane参考平面off-axis离轴shaded area阴影区clear area空白区perturbation扰动evolution渐变decay减弱unimodual matrix单位矩阵discrepancy相位差longitudinal mode index纵模指数resonance共振quantum electronics量子电子学phenomenon现象exploit利用spontaneous emission自发辐射initial初始的thermodynamic热力学inphase同相位的population inversion粒子数反转transparent透明的threshold阈值predominate over占主导地位的monochromaticity单色性spatical and temporal coherence时空相干性by virtue of利用directionality方向性superposition叠加pump rate泵浦速率shunt分流corona breakdown电晕击穿audacity畅通无阻versatile用途广泛的photoelectric effect光电效应quantum detector 量子探测器quantum efficiency量子效率vacuum photodiode真空光电二极管photoelectric work function光电功函数cathode阴极anode阳极formidable苛刻的恶光的irrespective无关的impinge撞击in turn依次capacitance电容photomultiplier光电信增管photoconductor光敏电阻junction photodiode结型光电二极管avalanche photodiode雪崩二极管shot noise 散粒噪声thermal noise热噪声1.In this chapter we consider Maxwell’s equations and what they reveal about the propagation of light in vacuum and in matter. We introduce the concept of photons and present their density of states.Since the density of states is a rather important property，not only for photons，we approach this quantity in a rather general way. We will use the density of states later also for other(quasi-) particles including systems of reduced dimensionality.In addition,we introduce the occupation probability of these states for various groups of particles.在本章中，我们讨论麦克斯韦方程和他们显示的有关光在真空中传播的问题。

神奇的事物英语作文In the vast expanse of the universe, there exist many enigmatic and marvellous things that baffle the human mind. These phenomena, often beyond the realm of scientific explanation, captivate us with their mysterious and captivating nature. From the grandeur of the northernlights to the enigmatic disappearances of objects, theworld is full of wonders that await discovery.One such phenomenon is the northern Lights, a natural light display in the sky, predominantly seen in the high latitudes of the Northern Hemisphere. This spectral display, also known as aurora borealis, is caused by the interaction of solar wind particles with the Earth's atmosphere. The resulting lights dance across the sky in a range of colours, creating a breathtaking spectacle that has fascinatedpeople for centuries.Another mysterious phenomenon is the Stonehenge, a prehistoric monument located in Wiltshire, England. Constructed around 2000 BC, the purpose of this circular structure of upright stones remains a mystery. Itsalignment with the sun and moon during certain times of theyear adds to its enigma, making it a popular destinationfor those seeking to unravel its secrets.The Bermuda Triangle, a region in the western part of the North Atlantic Ocean, is yet another enigmatic place. This triangular area, bordered by Florida, Bermuda, and Puerto Rico, has been the site of numerous unexplained disappearances of ships and aircraft. Despite numerous investigations, no conclusive evidence has been found to explain these mysterious disappearances.In the realm of the human body, there also exist神奇的事物。

Spectroscopic Study of the Interaction between Small Molecules and Large Proteins1. IntroductionThe study of drug-protein interactions is of great importance in drug discovery and development. Understanding how small molecules interact with proteins at the molecular level is crucial for the design of new and more effective drugs. Spectroscopic techniques have proven to be valuable tools in the investigation of these interactions, providing det本人led information about the binding affinity, mode of binding, and structural changes that occur upon binding.2. Spectroscopic Techniques2.1. Fluorescence SpectroscopyFluorescence spectroscopy is widely used in the study of drug-protein interactions due to its high sensitivity and selectivity. By monitoring the changes in the fluorescence emission of either the drug or the protein upon binding, valuable information about the binding affinity and the binding site can be obt本人ned. Additionally, fluorescence quenching studies can provide insights into the proximity and accessibility of specific amino acid residues in the protein's binding site.2.2. UV-Visible SpectroscopyUV-Visible spectroscopy is another powerful tool for the investigation of drug-protein interactions. This technique can be used to monitor changes in the absorption spectra of either the drug or the protein upon binding, providing information about the binding affinity and the stoichiometry of the interaction. Moreover, UV-Visible spectroscopy can be used to study the conformational changes that occur in the protein upon binding to the drug.2.3. Circular Dichroism SpectroscopyCircular dichroism spectroscopy is widely used to investigate the secondary structure of proteins and to monitor conformational changes upon ligand binding. By analyzing the changes in the CD spectra of the protein in the presence of the drug, valuable information about the structural changes induced by the binding can be obt本人ned.2.4. Nuclear Magnetic Resonance SpectroscopyNMR spectroscopy is a powerful technique for the investigation of drug-protein interactions at the atomic level. By analyzing the chemical shifts and the NOE signals of the protein in thepresence of the drug, det本人led information about the binding site and the mode of binding can be obt本人ned. Additionally, NMR can provide insights into the dynamics of the protein upon binding to the drug.3. Applications3.1. Drug DiscoverySpectroscopic studies of drug-protein interactions play a crucial role in drug discovery, providing valuable information about the binding affinity, selectivity, and mode of action of potential drug candidates. By understanding how small molecules interact with their target proteins, researchers can design more potent and specific drugs with fewer side effects.3.2. Protein EngineeringSpectroscopic techniques can also be used to study the effects of mutations and modifications on the binding affinity and specificity of proteins. By analyzing the binding of small molecules to wild-type and mutant proteins, valuable insights into the structure-function relationship of proteins can be obt本人ned.3.3. Biophysical StudiesSpectroscopic studies of drug-protein interactions are also valuable for the characterization of protein-ligandplexes, providing insights into the thermodynamics and kinetics of the binding process. Additionally, these studies can be used to investigate the effects of environmental factors, such as pH, temperature, and ionic strength, on the stability and binding affinity of theplexes.4. Challenges and Future DirectionsWhile spectroscopic techniques have greatly contributed to our understanding of drug-protein interactions, there are still challenges that need to be addressed. For instance, the study of membrane proteins and protein-protein interactions using spectroscopic techniques rem本人ns challenging due to theplexity and heterogeneity of these systems. Additionally, the development of new spectroscopic methods and the integration of spectroscopy with other biophysical andputational approaches will further advance our understanding of drug-protein interactions.In conclusion, spectroscopic studies of drug-protein interactions have greatly contributed to our understanding of how small molecules interact with proteins at the molecular level. Byproviding det本人led information about the binding affinity, mode of binding, and structural changes that occur upon binding, spectroscopic techniques have be valuable tools in drug discovery, protein engineering, and biophysical studies. As technology continues to advance, spectroscopy will play an increasingly important role in the study of drug-protein interactions, leading to the development of more effective and targeted therapeutics.。

IEEE Std1241-2000 IEEE Standard for Terminology and Test Methods for Analog-to-Digital ConvertersSponsorWaveform Measurement and Analysis Technical Committeeof theof theIEEE Instrumentation and Measurement SocietyApproved7December2000IEEE-SA Standards BoardAbstract:IEEE Std1241-2000identifies analog-to-digital converter(ADC)error sources and provides test methods with which to perform the required error measurements.The information in this standard is useful both to manufacturers and to users of ADCs in that it provides a basis for evaluating and comparing existing devices,as well as providing a template for writing specifications for the procurement of new ones.In some applications,the information provided by the tests described in this standard can be used to correct ADC errors, e.g.,correction for gain and offset errors.This standard also presents terminology and definitions to aid the user in defining and testing ADCs.Keywords:ADC,A/D converter,analog-to-digital converter,digitizer,terminology,test methodsThe Institute of Electrical and Electronics Engineers,Inc.3Park Avenue,New York,NY10016-5997,USACopyrightß2001by the Institute of Electrical and Electronics Engineers,Inc.All rights reserved. Published 13 June 2001. Printed in the United States of America.Print:ISBN0-7381-2724-8SH94902PDF:ISBN0-7381-2725-6SS94902No part of this publication may be reproduced in any form,in an electronic retrieval system or otherwise,without the prior written permission of the publisher.IEEE Standards documents are developed within the IEEE Societies and the Standards Coordinating Committees of the IEEE Standards Association(IEEE-SA)Standards Board.The IEEE develops its standards through a consensus development process,approved by the American National Standards Institute,which brings together volunteers representing varied viewpoints and interests to achieve thefinal product.Volunteers are not necessarily members of the Institute and serve without compensation.While the IEEE administers the process and establishes rules to promote fairness in the consensus development process,the IEEE does not independently evaluate,test,or verify the accuracy of any of the information contained in its standards.Use of an IEEE Standard is wholly voluntary.The IEEE disclaims liability for any personal injury,property or other damage,of any nature whatsoever,whether special,indirect,consequential,or compensatory,directly or indirectly resulting from the publication,use of,or reliance upon this,or any other IEEE Standard document.The IEEE does not warrant or represent the accuracy or content of the material contained herein,and expressly disclaims any express or implied warranty,including any implied warranty of merchantability orfitness for a specific purpose,or that the use of the material contained herein is free from patent infringement.IEEE Standards documents are supplied‘‘AS IS.’’The existence of an IEEE Standard does not imply that there are no other ways to produce,test,measure,purchase, market,or provide other goods and services related to the scope of the IEEE Standard.Furthermore,the viewpoint expressed at the time a standard is approved and issued is subject to change brought about through developments in the state of the art and comments received from users of the standard.Every IEEE Standard is subjected to review at least everyfive years for revision or reaffirmation.When a document is more thanfive years old and has not been reaffirmed,it is reasonable to conclude that its contents,although still of some value,do not wholly reflect the present state of the art. Users are cautioned to check to determine that they have the latest edition of any IEEE Standard.In publishing and making this document available,the IEEE is not suggesting or rendering professional or other services for,or on behalf of,any person or entity.Nor is the IEEE undertaking to perform any duty owed by any other person or entity to another.Any person utilizing this,and any other IEEE Standards document,should rely upon the advice of a competent professional in determining the exercise of reasonable care in any given circumstances.Interpretations:Occasionally questions may arise regarding the meaning of portions of standards as they relate to specific applications.When the need for interpretations is brought to the attention of IEEE,the Institute will initiate action to prepare appropriate responses.Since IEEE Standards represent a consensus of concerned interests,it is important to ensure that any interpretation has also received the concurrence of a balance of interests.For this reason, IEEE and the members of its societies and Standards Coordinating Committees are not able to provide an instant response to interpretation requests except in those cases where the matter has previously received formal consideration. Comments for revision of IEEE Standards are welcome from any interested party,regardless of membership affiliation with IEEE.Suggestions for changes in documents should be in the form of a proposed change of text,together with appropriate supporting ments on standards and requests for interpretations should be addressed to:Secretary,IEEE-SA Standards Board445Hoes LaneP.O.Box1331Piscataway,NJ08855-1331USANote:Attention is called to the possibility that implementation of this standard may require use of subjectmatter covered by patent rights.By publication of this standard,no position is taken with respect to theexistence or validity of any patent rights in connection therewith.The IEEE shall not be responsible foridentifying patents for which a license may be required by an IEEE standard or for conducting inquiriesinto the legal validity or scope of those patents that are brought to its attention.IEEE is the sole entity that may authorize the use of certification marks,trademarks,or other designations to indicate compliance with the materials set forth herein.Authorization to photocopy portions of any individual standard for internal or personal use is granted by the Institute of Electrical and Electronics Engineers,Inc.,provided that the appropriate fee is paid to Copyright Clearance Center. To arrange for payment of licensing fee,please contact Copyright Clearance Center,Customer Service,222Rosewood Drive,Danvers,MA01923USA;(978)750-8400.Permission to photocopy portions of any individual standard for educational classroom use can also be obtained through the Copyright Clearance Center.Introduction(This introduction is not a part of IEEE Std1241-2000,IEEE Standard for Terminology and Test Methods for Analog-to-Digital Converters.)This standard defines the terms,definitions,and test methods used to specify,characterize,and test analog-to-digital converters(ADCs).It is intended for the following:—Individuals and organizations who specify ADCs to be purchased—Individuals and organizations who purchase ADCs to be applied in their products —Individuals and organizations whose responsibility is to characterize and write reports on ADCs available for use in specific applications—Suppliers interested in providing high-quality and high-performance ADCs to acquirersThis standard is designed to help organizations and individuals—Incorporate quality considerations during the definition,evaluation,selection,and acceptance of supplier ADCs for operational use in their equipment—Determine how supplier ADCs should be evaluated,tested,and accepted for delivery to end users This standard is intended to satisfy the following objectives:—Promote consistency within organizations in acquiring third-party ADCs from component suppliers—Provide useful practices on including quality considerations during acquisition planning —Provide useful practices on evaluating and qualifying supplier capabilities to meet user requirements—Provide useful practices on evaluating and qualifying supplier ADCs—Assist individuals and organizations judging the quality and suitability of supplier ADCs for referral to end usersSeveral standards have previously been written that address the testing of analog-to-digital converters either directly or indirectly.These include—IEEE Std1057-1994a,which describes the testing of waveform recorders.This standard has been used as a guide for many of the techniques described in this standard.—IEEE Std746-1984[B16]b,which addresses the testing of analog-to-digital and digital-to-analog converters used for PCM television video signal processing.—JESD99-1[B21],which deals with the terms and definitions used to describe analog-to-digital and digital-to-analog converters.This standard does not include test methods.IEEE Std1241-2000for analog-to-digital converters is intended to focus specifically on terms and definitions as well as test methods for ADCs for a wide range of applications.a Information on references can be found in Clause2.b The numbers in brackets correspond to those in the bibliography in Annex C.As of October2000,the working group had the following membership:Steve Tilden,ChairPhilip Green,Secretary&Text EditorW.Thomas Meyer,Figures EditorPasquale Arpaia Giovanni Chiorboli Tom Linnenbrink*B.N.Suresh Babu Pasquale Daponte Solomon MaxAllan Belcher David Hansen Carlo MorandiDavid Bergman Fred Irons Bill PetersonEric Blom Dan Kien Pierre-Yves RoyDan Knierim*Chairman,TC-10CommitteeContributions were also made in prior years by:Jerry Blair John Deyst Norris NahmanWilliam Boyer Richard Kromer Otis M.SolomonSteve Broadstone Yves Langard T.Michael SoudersThe following members of the balloting committee voted on this standard:Pasquale Arpaia Pasquale Daponte W.Thomas MeyerSuresh Babu Philip Green Carlo MorandiEric Blom Fred Irons William E.PetersonSteven Broadstone Dan Knierim Pierre-Yves RoyGiovanni Chiorboli T.E.Linnenbrink Steven J.TildenSolomon MaxWhen the IEEE-SA Standards Board approved this standard on21September2000,it had the following membership:Donald N.Heirman,ChairJames T.Carlo,Vice-ChairJudith Gorman,SecretarySatish K.Aggarwal James H.Gurney James W.MooreMark D.Bowman Richard J.Holleman Robert F.MunznerGary R.Engmann Lowell G.Johnson Ronald C.PetersenHarold E.Epstein Robert J.Kennelly Gerald H.Petersonndis Floyd Joseph L.Koepfinger*John B.PoseyJay Forster*Peter H.Lips Gary S.RobinsonHoward M.Frazier L.Bruce McClung Akio TojoRuben D.Garzon Daleep C.Mohla Donald W.Zipse*Member EmeritusAlso included are the following nonvoting IEEE-SA Standards Board liaisons:Alan Cookson,NIST RepresentativeDonald R.Volzka,TAB RepresentativeDon MessinaIEEE Standards Project EditorContents1.Overview (1)1.1Scope (1)1.2Analog-to-digital converter background (2)1.3Guidance to the user (3)1.4Manufacturer-supplied information (5)2.References (7)3.Definitions and symbols (7)3.1Definitions (7)3.2Symbols and acronyms (14)4.Test methods (18)4.1General (18)4.2Analog input (41)4.3Static gain and offset (43)4.4Linearity (44)4.5Noise(total) (51)4.6Step response parameters (63)4.7Frequency response parameters (66)4.8Differential gain and phase (71)4.9Aperture effects (76)4.10Digital logic signals (78)4.11Pipeline delay (78)4.12Out-of-range recovery (78)4.13Word error rate (79)4.14Differential input specifications (81)4.15Comments on reference signals (82)4.16Power supply parameters (83)Annex A(informative)Comment on errors associated with word-error-rate measurement (84)Annex B(informative)Testing an ADC linearized with pseudorandom dither (86)Annex C(informative)Bibliography (90)IEEE Standard for Terminology and Test Methods for Analog-to-Digital Converters1.OverviewThis standard is divided into four clauses plus annexes.Clause1is a basic orientation.For further investigation,users of this standard can consult Clause2,which contains references to other IEEE standards on waveform measurement and relevant International Standardization Organization(ISO) documents.The definitions of technical terms and symbols used in this standard are presented in Clause3.Clause4presents a wide range of tests that measure the performance of an analog-to-digital converter.Annexes,containing the bibliography and informative comments on the tests presented in Clause4,augment the standard.1.1ScopeThe material presented in this standard is intended to provide common terminology and test methods for the testing and evaluation of analog-to-digital converters(ADCs).This standard considers only those ADCs whose output values have discrete values at discrete times,i.e., they are quantized and sampled.In general,this quantization is assumed to be nominally uniform(the input–output transfer curve is approximately a straight line)as discussed further in 1.3,and the sampling is assumed to be at a nominally uniform rate.Some but not all of the test methods in this standard can be used for ADCs that are designed for non-uniform quantization.This standard identifies ADC error sources and provides test methods with which to perform the required error measurements.The information in this standard is useful both to manufacturers and to users of ADCs in that it provides a basis for evaluating and comparing existing devices,as well as providing a template for writing specifications for the procurement of new ones.In some applications, the information provided by the tests described in this standard can be used to correct ADC errors, e.g.,correction for gain and offset errors.The reader should note that this standard has many similarities to IEEE Std1057-1994.Many of the tests and terms are nearly the same,since ADCs are a necessary part of digitizing waveform recorders.IEEEStd1241-2000IEEE STANDARD FOR TERMINOLOGY AND TEST METHODS 1.2Analog-to-digital converter backgroundThis standard considers only those ADCs whose output values have discrete values at discrete times, i.e.,they are quantized and sampled.Although different methods exist for representing a continuous analog signal as a discrete sequence of binary words,an underlying model implicit in many of the tests in this standard assumes that the relationship between the input signal and the output values approximates the staircase transfer curve depicted in Figure1a.Applying this model to a voltage-input ADC,the full-scale input range(FS)at the ADC is divided into uniform intervals,known as code bins, with nominal width Q.The number of code transition levels in the discrete transfer function is equal to 2NÀ1,where N is the number of digitized bits of the ADC.Note that there are ADCs that are designed such that N is not an integer,i.e.,the number of code transition levels is not an integral power of two. Inputs below thefirst transition or above the last transition are represented by the most negative and positive output codes,respectively.Note,however,that two conventions exist for relating V min and V max to the nominal transition points between code levels,mid-tread and mid-riser.The dotted lines at V min,V max,and(V minþV max)/2indicate what is often called the mid-tread convention,where thefirst transition is Q/2above V min and the last transition is3Q/2,below V max. This convention gets its name from the fact that the midpoint of the range,(V minþV max)/2,occurs in the middle of a code,i.e.,on the tread of the staircase transfer function.The second convention,called the mid-riser convention,is indicated in thefigure by dashed lines at V min,V max,and(V minþV max)/2. In this convention,V min isÀQ from thefirst transition,V max isþQ from the last transition,and the midpoint,(V minþV max)/2,occurs on a staircase riser.The difference between the two conventions is a displacement along the voltage axis by an amount Q/2.For all tests in this standard,this displacement has no effect on the results and either convention may be used.The one place where it does matter is when a device provides or expects user-provided reference signals.In this case the manufacturer must provide the necessary information relating the reference levels to the code transitions.In both conventions the number of code transitions is 2NÀ1and the full-scale range,FSR,is from V min to V max.Even in an ideal ADC,the quantization process produces errors.These errors contribute to the difference between the actual transfer curve and the ideal straight-line transfer curve,which is plotted as a function of the input signal in Figure1b.To use this standard,the user must understand how the transfer function maps its input values to output codewords,and how these output codewords are converted to the code bin numbering convention used in this standard.As shown in Figure1a,the lowest code bin is numbered0, the next is1,and so on up to the highest code bin,numbered(2NÀ1).In addition to unsigned binary(Figure1a),ADCs may use2’s complement,sign-magnitude,Gray,Binary-Coded-Decimal (BCD),or other output coding schemes.In these cases,a simple mapping of the ADC’s consecutive output codes to the unsigned binary codes can be used in applying various tests in this standard.Note that in the case of an ADC whose number of distinct output codes is not an integral power of2(e.g.,a BCD-coded ADC),the number of digitized bits N is still defined,but will not be an integer.Real ADCs have other errors in addition to the nominal quantization error shown in Figure1b.All errors can be divided into the categories of static and dynamic,depending on the rate of change of the input signal at the time of digitization.A slowly varying input can be considered a static signal if its effects are equivalent to those of a constant signal.Static errors,which include the quantization error, usually result from non-ideal spacing of the code transition levels.Dynamic errors occur because of additional sources of error induced by the time variation of the analog signal being sampled.Sources include harmonic distortion from the analog input stages,signal-dependent variations in the time of samples,dynamic effects in internal amplifier and comparator stages,and frequency-dependent variation in the spacing of the quantization levels.1.3Guidance to the user1.3.1InterfacingADCs present unique interfacing challenges,and without careful attention users can experience substandard results.As with all mixed-signal devices,ADCs perform as expected only when the analog and digital domains are brought together in a well-controlled fashion.The user should fully understand the manufacturer’s recommendations with regard to proper signal buffering and loading,input signal connections,transmission line matching,circuit layout patterns,power supply decoupling,and operating conditions.Edge characteristics for start-convert pulse(s)and clock(s)must be carefully chosen to ensure that input signal purity is maintained with sufficient margin up to the analog input pin(s).Most manufacturers now provide excellent ADC evaluation boards,which demonstrate IN P U T IN P U T(a)Figure 1—Staircase ADC transfer function,having full-scale range FSR and 2N À1levels,corresponding to N -bit quantizationIEEE FOR ANALOG-TO-DIGITAL CONVERTERS Std 1241-2000IEEEStd1241-2000IEEE STANDARD FOR TERMINOLOGY AND TEST METHODS recommended layout techniques,signal conditioning,and interfacing for their ADCs.If the characteristics of a new ADC are not well understood,then these boards should be analyzed or used before starting a new layout.1.3.2Test conditionsADC test specifications can be split into two groups:test conditions and test results.Typical examples of the former are:temperature,power supply voltages,clock frequency,and reference voltages. Examples of the latter are:power dissipation,effective number of bits,spurious free dynamic range (SFDR),and integral non-linearity(INL).The test methods defined in this standard describe the measurement of test results for given test conditions.ADC specification sheets will often give allowed ranges for some test condition(e.g.,power supply ranges).This implies that the ADC will function properly and that the test results will fall within their specified ranges for all test conditions within their specified ranges.Since the test condition ranges are generally specified in continuous intervals,they describe an infinite number of possible test conditions,which obviously cannot be exhaustively tested.It is up to the manufacturer or tester of an ADC to determine from design knowledge and/or testing the effect of the test conditions on the test result,and from there to determine the appropriate set of test conditions needed to accurately characterize the range of test results.For example,knowledge of the design may be sufficient to know that the highest power dissipation(test result)will occur at the highest power supply voltage(test condition),so the power dissipation test need be run only at the high end of the supply voltage range to check that the dissipation is within the maximum of its specified range.It is very important that relevant test conditions be stated when presenting test results.1.3.3Test equipmentOne must ensure that the performance of the test equipment used for these tests significantly exceeds the desired performance of the ADC under ers will likely need to include additional signal conditioning in the form offilters and pulse shapers.Accessories such as terminators, attenuators,delay lines,and other such devices are usually needed to match signal levels and to provide signal isolation to avoid corrupting the input stimuli.Quality testing requires following established procedures,most notably those specified in ISO9001: 2000[B18].In particular,traceability of instrumental calibration to a known standard is important. Commonly used test setups are described in4.1.1.1.3.4Test selectionWhen choosing which parameters to measure,one should follow the outline and hints in this clause to develop a procedure that logically and efficiently performs all needed tests on each unique setup. The standard has been designed to facilitate the development of these test procedures.In this standard the discrete Fourier transform(DFT)is used extensively for the extraction of frequency domain parameters because it provides numerous evaluation parameters from a single data record.DFT testing is the most prevalent technique used in the ADC manufacturing community,although the sine-fit test, also described in the standard,provides meaningful data.Nearly every user requires that the ADC should meet or exceed a minimum signal-to-noise-and-distortion ratio(SINAD)limit for the application and that the nonlinearity of the ADC be well understood.Certainly,the extent to whichthis standard is applied will depend upon the application;hence,the procedure should be tailored for each unique characterization plan.1.4Manufacturer-supplied information1.4.1General informationManufacturers shall supply the following general information:a)Model numberb)Physical characteristics:dimensions,packaging,pinoutsc)Power requirementsd)Environmental conditions:Safe operating,non-operating,and specified performance tempera-ture range;altitude limitations;humidity limits,operating and storage;vibration tolerance;and compliance with applicable electromagnetic interference specificationse)Any special or peculiar characteristicsf)Compliance with other specificationsg)Calibration interval,if required by ISO10012-2:1997[B19]h)Control signal characteristicsi)Output signal characteristicsj)Pipeline delay(if any)k)Exceptions to the above parameters where applicable1.4.2Minimum specificationsThe manufacturer shall provide the following specifications(see Clause3for definitions):a)Number of digitized bitsb)Range of allowable sample ratesc)Analog bandwidthd)Input signal full-scale range with nominal reference signal levelse)Input impedancef)Reference signal levels to be appliedg)Supply voltagesh)Supply currents(max,typ)i)Power dissipation(max,typ)1.4.3Additional specificationsa)Gain errorb)Offset errorc)Differential nonlinearityd)Harmonic distortion and spurious responsee)Integral nonlinearityf)Maximum static errorg)Signal-to-noise ratioh)Effective bitsi)Random noisej)Frequency responsek)Settling timel)Transition duration of step response(rise time)m)Slew rate limitn)Overshoot and precursorso)Aperture uncertainty(short-term time-base instability)p)Crosstalkq)Monotonicityr)Hysteresiss)Out-of-range recoveryt)Word error rateu)Common-mode rejection ratiov)Maximum common-mode signal levelw)Differential input impedancex)Intermodulation distortiony)Noise power ratioz)Differential gain and phase1.4.4Critical ADC parametersTable1is presented as a guide for many of the most common ADC applications.The wide range of ADC applications makes a comprehensive listing impossible.This table is intended to be a helpful starting point for users to apply this standard to their particular applications.Table1—Critical ADC parametersTypical applications Critical ADC parameters Performance issuesAudio SINAD,THD Power consumption.Crosstalk and gain matching.Automatic control MonotonicityShort-term settling,long-term stability Transfer function. Crosstalk and gain matching. Temperature stability.Digital oscilloscope/waveform recorder SINAD,ENOBBandwidthOut-of-range recoveryWord error rateSINAD for wide bandwidthamplitude resolution.Low thermal noise for repeatability.Bit error rate.Geophysical THD,SINAD,long-term stability Millihertz response.Image processing DNL,INL,SINAD,ENOBOut-of-range recoveryFull-scale step response DNL for sharp-edge detection. High-resolution at switching rate. Recovery for blooming.Radar and sonar SINAD,IMD,ENOBSFDROut-of-range recovery SINAD and IMD for clutter cancellation and Doppler processing.Spectrum analysis SINAD,ENOBSFDR SINAD and SFDR for high linear dynamic range measurements.Spread spectrum communication SINAD,IMD,ENOBSFDR,NPRNoise-to-distortion ratioIMD for quantization of smallsignals in a strong interferenceenvironment.SFDR for spatialfiltering.NPR for interchannel crosstalk.Telecommunication personal communications SINAD,NPR,SFDR,IMDBit error rateWord error rateWide input bandwidth channel bank.Interchannel crosstalk.Compression.Power consumption.Std1241-2000IEEE STANDARD FOR TERMINOLOGY AND TEST METHODS2.ReferencesThis standard shall be used in conjunction with the following publications.When the following specifications are superseded by an approved revision,the revision shall apply.IEC 60469-2(1987-12),Pulse measurement and analysis,general considerations.1IEEE Std 1057-1994,IEEE Standard for Digitizing Waveform Recorders.23.Definitions and symbolsFor the purposes of this standard,the following terms and definitions apply.The Authoritative Dictionary of IEEE Standards Terms [B15]should be referenced for terms not defined in this clause.3.1Definitions3.1.1AC-coupled analog-to-digital converter:An analog-to-digital converter utilizing a network which passes only the varying ac portion,not the static dc portion,of the analog input signal to the quantizer.3.1.2alternation band:The range of input levels which causes the converter output to alternate between two adjacent codes.A property of some analog-to-digital converters,it is the complement of the hysteresis property.3.1.3analog-to-digital converter (ADC):A device that converts a continuous time signal into a discrete-time discrete-amplitude signal.3.1.4aperture delay:The delay from a threshold crossing of the analog-to-digital converter clock which causes a sample of the analog input to be taken to the center of the aperture for that sample.COMINT ¼communications intelligence DNL ¼differential nonlinearity ENOB ¼effective number of bits ELINT ¼electronic intelligence NPR ¼noise power ratio INL ¼integral nonlinearity DG ¼differential gain errorSIGINT ¼signal intelligenceSINAD ¼signal-to-noise and distortion ratio THD ¼total harmonic distortion IMD ¼intermodulation distortion SFDR ¼spurious free dynamic range DP ¼differential phase errorTable 1—Critical ADC parameters (continued)Typical applicationsCritical ADC parametersPerformance issuesVideoDNL,SINAD,SFDR,DG,DP Differential gain and phase errors.Frequency response.Wideband digital receivers SIGINT,ELINT,COMINTSFDR,IMD SINADLinear dynamic range fordetection of low-level signals in a strong interference environment.Sampling frequency.1IEC publications are available from IEC Sales Department,Case Postale 131,3rue de Varemb,CH 1211,Gen ve 20,Switzerland/Suisse (http://www.iec.ch).IEC publications are also available in the United States from the Sales Department,American National Standards Institute,25W.43rd Street,Fourth Floor,New York,NY 10036,USA ().2IEEE publications are available from the Institute of Electrical and Electronics Engineers,445Hoes Lane,P.O.Box 1331,Piscataway,NJ 08855-1331,USA (/).。

Excited Doublet States of Electrochemically Generated Aromatic Imide and Diimide Radical AnionsDavid Gosztola,*Mark P.Niemczyk,and Walter SvecChemistry Di V ision,Argonne National Laboratory,Argonne,Illinois60439-4831Aaron S.Lukas and Michael R.Wasielewski*,†Department of Chemistry,Northwestern Uni V ersity,E V anston,Illinois60208-3113Recei V ed:February22,2000;In Final Form:May17,2000The radical anions of aromatic diimides have been implicated recently in a wide variety of photochemicalelectron transfer reactions.Photoexcitation of these radical anions produces powerfully reducing species.Yet,the properties of theπ*excited doublet states of these organic radical anions remain obscure.The radicalanions of three aromatic imides with increasingly largerπsystems,N-(2,5-di-tert-butylphenyl)phthalimide,1,N-(2,5-di-tert-butylphenyl)-1,8-naphthalimide,2,and N-(2,5-di-tert-butylphenyl)perylene-3,4-dicarboximide,3,as well as the three corresponding aromatic diimides,N,N′-bis(2,5-di-tert-butylphenyl)pyromellitimide,4a,N,N′-bis(2,5-di-tert-butylphenyl)-naphthalene-1,8:4,5-tetracarboxydiimide,5a,and N,N′-bis(2,5-di-tert-butylphenyl)perylene-3,4:9,10-tetracarboxydiimide,6,were produced by electrochemical reduction of the neutralmolecules in an optically transparent thin layer electrochemical cell.The radical anions of these imides anddiimides all exhibit intense visible and weaker near-IR absorption bands corresponding to their D0f D ntransitions.Excited states of the radical anions were generated by subpicosecond excitation into these absorptionbands.Excitation of1•-and2•-resulted in decomposition of these radical anions,whereas excitation of3•--6•-yielded transient spectra of their D1f D n transitions and the lifetimes of D1.The lifetimes of the D1excited states of the radical anions of3•--6•-are all less than600ps and increase as the D0-D1energy gapincreases.These results impose design constraints on the use of these excited radical anions as electron donorsin electron-transfer systems targeted toward molecular electronics and solar energy conversion.IntroductionPhotoexcited radical ions have been shown to be powerful redox agents in mechanistic and electron-transfer studies.1-8 Spectroscopic techniques such as fluorescence and transient absorption have been used to directly probe the photophysical properties of radical ion excited states and have shown that these properties are very different from those of the neutral parent molecule.7-19In some cases it has been found that the excited states of radical ions of highly fluorescent molecules are themselves either weakly fluorescent or nonfluorescent.4,14,20 This property has recently been exploited to implement an optical molecular switch concept.21Many studies of radical ion excited states have involved quinone or quinone-like molecules in which the radical anion is produced either electrochemically or pulse radiolytically.One of the reasons quinone radical anions have received so much attention is their role as electron acceptors in numerous donor-acceptor molecules designed to mimic photosynthetic charge separation.22Excited quinone radical anions have been implicated as the products of highly exoergic electron-transfer reactions.23Nevertheless,the excited states of organic radical anions have not been studied widely in condensed media.Aromatic diimides have been used as electron acceptors in many fundamental studies of photoinduced electron-transfer including models for photosynthesis,24-28solar energy conver-sion,29molecular electronics,30electrochromic devices,31,32and photorefractive materials.33,34These molecules have been widely used in electron-transfer studies because they undergo reversible one-electron reduction at modest potentials to form stable radical anions.In addition,the radical anions of most aromatic diimides are good chromophores with intense and characteristic visible and near-infrared(NIR)absorption bands,which aid in their unambiguous identification.The diimides studied here also possess stable doubly reduced dianions with properties that differ from either their neutral or radical anion precursors.The electrochemical and photophysical properties of some aromatic mono-,di-,and polyimides have been previously reported;35-38 however,very little is known about the excited states of the radical anions of these important electron acceptors.We have therefore undertaken a systematic study of the excited doublet states of the radical anions within a series of aromatic imides and diimides.Results and DiscussionElectrochemistry.The cyclic voltammograms for all of the compounds showed two quasi-reversible(∆E p(anodic-cathodic) 59-88mV at50mV‚s-1),well-separated one-electron reduc-tion waves.Table1lists the measured half-wave reduction potentials for radical anion(E-1/2)and dianion(E2-1/2)forma-tion.The reduction potentials for molecules1-6(Chart1)are all in agreement with previously reported values of the same or very similar compounds.31,35-37,39As previously noted,within the imide and diimide series the first and second reduction potentials become more positive as the core aromatic ring system†E-mail:wasielew@.6545 J.Phys.Chem.A2000,104,6545-655110.1021/jp000706f CCC:$19.00©2000American Chemical SocietyPublished on Web06/24/2000becomes larger.35In addition,the reduction potentials of thediimides are all more positive than those of the monoimides.Furthermore,within each series,the difference between the firstand second reduction potential(∆E0)E2-1/2-E-1/2)becomessmaller with increased core size.31These two observationsindicate that the more extendedπsystems have larger elec-tron affinities and diminished Coulombic repulsion between thefirst and second electrons added to the ring system duringreduction.Radical Anion and Dianion Spectra.Ground-state absorp-tion spectra of the radical anions of1-3are shown in Figure1,while absorption spectra of the neutral(N),radical anion(R•-),and dianion(R2-)states of4-6are shown in Figure2.Wavelengths and extinction coefficients of the major absorptionbands for the various oxidation states are listed in Table2.Bulkelectrolysis from N f R•-f R2-f N for diimides4-6is almost completely reversible with greater than90%recoveryof N after more than30min at the most negative potentials.Most of the loss is probably due to reactions with residualoxygen within the optically transparent,thin layer electrochemi-cal(OTTLE)cell,although some loss,especially duringpotential excursions to the dianion states,may be due tophotodegradation(vide infra).Bulk electrochemical reductionof monoimides1-3to R•-is found to be somewhat lessreversible than is observed for the diimides.Again,the partialirreversibility is probably due to scavenging by oxygen orphotodegradation and the fact that the first reduction potentialfor the monoimides is consistently more negative than even the second reduction potential of the diimides.Extinction coef-ficients for the R•-absorption bands are calculated by compar-ing peak intensity ratios between the growing R•-and decaying N absorption bands during the first electroreduction step. Likewise,extinction coefficients for the R2-absorption bands are calculated by comparing peak intensity ratios between the growing R2-and decaying R•-bands during the second electroreduction step.The0.27-0.66V separation between E-1/2and E2-1/2permitted bulk reduction to be carried out in two discrete steps.This was confirmed by the detection of at least one isosbestic point during the formation of R•-in all of the compounds except1and4,which are the only compounds in which there is no spectral overlap between the N and R•-oxidation states.During the second reduction step,new isos-bestic points were detected for4-6as R2-was formed. Upon formation of R•-,the absorption spectra of all of the compounds show new bands throughout the visible and NIR.TABLE1:Redox Potentials(V vs SCE)compd E-1/2E2-1/2E2-1/2-E-1/21-1.4036-2.30360.902a-1.3653a-0.96-1.550.594a,b b-0.71-1.370.665a,b b-0.48-0.990.516b-0.43-0.700.27a Butyronitrile+0.1M Bu4NPF6.b DMF+0.1M Bu4NPF6.CHART1Figure1.Ground-state absorption spectra of electrochemically gener-ated radical anions of1-3in DMF+0.1M Bu4NPF6.Figure2.Ground-state absorption spectra of neutral,radical anion,and dianion forms of4b,5a,and6in DMF+0.1M Bu4NPF6. 6546J.Phys.Chem.A,Vol.104,No.28,2000Gosztola et al.In general,all of the R•-spectra share a number of similari-ties:at least one long wavelength(>700nm)absorption,whichhas been assigned to the D0f D1,transition of the radical anion,35,36intense transitions with extinction coefficients equalto or greater than those of the neutral compound,and complexvibronic structure on the absorption bands.Similar generaliza-tions can be made with regard to the dianion spectra of4-6with the notable exception that no NIR absorption bands arepresent at wavelengths<1100nm.The singlet-singlet transi-tions in the dianions occur at higher energies than the doublet-doublet transitions in the radical anions.To aid in interpreting the radical anion and dianion spectra,especially with regard to identifying the lowest energy transi-tions,molecular orbital calculations were performed.Wecalculated energy minimized ground-state structures of theradical anions and dianions of the N,N′-dimethyl-substitutedanalogues of1-6using semiempirical unrestricted and restrictedHartree-Fock PM3methods,respectively.The energy-mini-mized structures were then subjected to a ZINDO/S calculationwith CI to determine the electronic transition energies.Thesedata are given in Table3.The radical anions all possess low-energy transitions that correspond to D0f D1.Moreover,both the number and intensities of the predicted allowed transitions are in reasonable agreement with the observed radical anionspectra.The predicted transition energies for the diimides agree reasonably well with experiment,while those for the monoim-ides agree less so.Within the series of monoimides,the MO calculations predict D0f D1transitions with modest intensities in the NIR.Low-energy absorption bands are observed for2•-and3•-at832 and818nm,respectively.These bands correspond to the calculated transitions at957and836nm for the N-methyl derivatives of2•-and3•-,respectively,and are thus assigned to this transition.The lowest energy transition predicted for1•-at1037nm is weak and is not observed experimentally. However,the spectrum of1•-shown in Figure1displays a slight increase in the baseline at NIR wavelengths.If one compares the energy differences between the predicted electronic transitions for the diimides with the corresponding energy differences in the observed spectra,the agreement is good.This gives us confidence to assign the observed777and 955nm bands in5a•-and6•-respectively to their D0f D1 transitions.The calculations predict that the D0f D1transition in4•-should be very weak at best,so that the intense bandTABLE2:Photophysical Propertiescompd N:λ(nm)( (M-1cm-1))R•-:λ(nm)( (M-1cm-1))R2-:λ(nm)( (M-1cm-1))1*N:τ(ps)2*R•-:τ(ps) 1260(15600)18544419(3470)362335(12500)38272(15500)<5042350(10647)420(23500)491(3000)746(2200)832(4000)3489(35300)55588(68000)3500(100533(57 512(33590)768(11000)818(8500)4a406(2700)6(2652(9800)718(41700)364b418(2700)516(23300)9(2649(9400)525(24200)715(41700)36552(144000)5a361(15100)474(26000)400(19500)141(7 381(16400)605(7200)423(26700)698(2400)520(2600)777(4100)563(6300)612(10600)5b382(14500)24474(23000)397(18400)<2043260(19605(6400)421(28400)683(2100)510(2300)755(3600)550(6600)597(11500)6458(19300)680(50600)532(42400)3800(100145(15 490(51000)700(79800)570(80000)526(80000)39712(74200)597(36700)766(21600)646(18100)795(49600)720(3400)955(28200)TABLE3:Calculated Electronic Transitions for RadicalAnions and Dianionsλmax(nm)(osc strength)compd radical anion dianionN-methylphthalimide257(0.135)370(0.356)559(0.133)600(0)1037(0.024)734(0.067)N-methyl-1,8-naphthalimide435(0.105)401(0.564)438(0)515(0.409)656(0.111)704(0.038)907(0.018)957(0.073)N-methylperylene-3,4-553(0.896)470(0.208)dicarboximide601(0.004)496(1.177)747(0.085)497(0.123)836(0.007)586(0.122)N,N′-dimethyl-396(0.142)514(0.960)pyromellitimide785(0.207)733(0)916(0)N,N′-dimethylnaphthalene-474(0.540)389(0.998)1,8:4,5-tetracarboxydiimide575(0.045)484(0)628(0)545(0.468)839(0.097)N,N′-dimethylperylene-615(1.090)429(0.116)3,4:9,10-tetracarboxydiimide724(0.105)436(0)851(0.014)492(1.510)526(0.370) Aromatic Imide and Diimide Radical Anions J.Phys.Chem.A,Vol.104,No.28,20006547observed at715nm is assigned to the allowed D0f D2 transition.Typically,for rigid aromatic molecules the absorption spectrum of theπ*excited state of the neutral molecule(1*N) strongly resembles that of the ground state of its radical anion (R•-).For example,1*3and3•-both have an absorption band around590nm,whereas1*6and6•-both have intense absorption bands around700nm.This similarity between the 1*N and R•-spectra can be attributed to the fact that both the S1f S n and D0f D n transitions involve the LUMO of N.In the case of1*N,the LUMO of N is populated by the initial photoexcitation of an electron from the HOMO of N.For R•-, the LUMO of N is populated by the one-electron electrochemical reduction of N forming the doublet ground state,D0,of R•-. While the optical transitions observed for1*N are S1f S n and the corresponding transitions for R•-are D0f D n,both sets of transitions occur at similar energies.This is a consequence of the fact that the energy of the LUMO of N is not changed greatly if it is occupied by either one or two electrons.Excitation of an electron from the LUMO of N to higher-lyingπorbitals of similar energy occurs as well.The rigidity of the molecules inhibits configurational mixing to some degree leading to spectra that can be analyzed by a zero-order consideration of the lowest populatedπorbitals.Table3also gives the calculated singlet-singlet electronic transitions for the dianions of1-6.The data for N-methyl12--32-are provided for completeness,but will not be discussed because the corresponding spectroelectrochemical data for12--32-could not be obtained due to the difficulty in producing thedianions by that method.The calculated singlet-singlet transi-tions for N,N′-dimethyl42--62-are in excellent agreement withthe corresponding experimental data for42--62-.For example,the intense transitions observed at421and597nm for5a2-are calculated to occur at389and545nm,respectively. Radical Anion Excited-State Spectra.Transient absorptionspectroscopy using150fs laser pulses was used to measure thetransient difference spectra and lifetimes of the radical anionexcited states(2*R•-)of compounds1-6.The radical anionexcited states were formed by exciting one of the intense D0f D n transitions of R•ser excitation of R•-was usually notdirected into the lowest energy,D0f D1,transition since the higher energy visible transitions often have much largerextinction coefficients than the NIR transitions and occur withinthe convenient tuning range of the pump laser.Excited-statetransient absorption difference spectra of3•--6•-are shownin Figure3.Radical anions3•--6•-were excited at590,715,605,and700nm,respectively.While scattered laser light distortsthe spectra to varying degrees at the pump wavelength,thetransient spectra at the other wavelengths consist primarily ofground-state bleaching bands with very little positive∆A.Forexample,the transient absorption spectrum of2*5a•-shown inFigure3exhibits a strong bleach of the474nm band of5a•-at12ps following excitation but only slight positive∆A changesnear650nm.However,in addition to their ground-statebleaching features,2*3•-and2*6•-also show strong positive∆A features below about500nm.The transient spectrum of each of the excited radical anions shows no evidence for formation of solvated electrons generated by means of photo-ionization of the radical anions.Radical Anion Excited-State Lifetimes.Although there havebeen relatively few direct measurements of the excited-statelifetimes of radical anions,it has been proposed that they willhave shorter lifetimes than the neutral parent due to the rela-tively small energy gap between the D0and D1states,giving rise to rapid and efficient nonradiative decay to the ground state.14,40Moreover,if the transitions areπ-π*in nature,their lifetimes may not be limited by symmetry considerations.The excited-state lifetimes of2*R•-were determined by monitoring both the recovery of the R•-ground state as well as the decay of the transient spectra due to2*R•-.The lifetimes measured for the excited states of the radical anions of3-6are listed in Table2.The subnanosecond excited-state lifetimes of the diimide radical anions may contribute to their exceptional photostability, since radical anion excited states are generally extraordinarily strong reducing agents.1,4For example,the oxidation potential for the excited doublet state2*4•-can be estimated41from the difference between the oxidation potential of the radical anion, -0.71V vs SCE,and the calculated energy of the D0f D1 transition,1.4eV,to give an oxidation potential of-2.1V vs SCE.Since the lifetime of2*4a•-is only6ps,its excited-state energy may dissipate before any intermolecular redox chemistry can occur.For1and2,the two most difficult to reduce compounds,the excited-state lifetimes of2*1•-and2*2•-could not be determined due to rapid decomposition of the excited radical anions.Even at pump energies as low as100nJ/pulse, the sample volume bleached in a matter of seconds.The design of the spectroelectrochemical cell used in these experiments is such that the only mass transport mechanism available to replenish the bleached sample volume is diffusion.Calculated as above,the oxidation potentials of2*1•-and2*2•-are about -2.7V vs SCE,a potential that may be sufficiently negative to rapidly reduce the solvent and/or the electrolyte.For compounds3-6,which were initially excited into higher-lying D n states,the R•-ground-state recovery time is the same as the2*R•-decay time indicating that rapid relaxation to the D1state within the doublet manifold of2*R•-occurs.In all cases, 2*R•-is formed with an instrument limited rise time and decays with a single-exponential time constant.For example,excitation Figure3.Transient absorption spectra of radical anions of4b,5a,6, and3.Pump wavelengths are indicated by the vertical arrows.The spectra are distorted at the pump wavelengths due to scattered laser light.Times are given for the delay of the probe beam relative to the excitation beam.6548J.Phys.Chem.A,Vol.104,No.28,2000Gosztola et al.of 6•-at its 700nm absorption band,which is three times more intense than its lowest energy D 0f D 1transition at 955nm,yields the same 145ps time constant independent of whether its bleach recovery at 670nm or its small positive ∆A at 465nm is monitored,Figure 4.These results show that internal conversion from higher-lying D n states occurs rapidly in these molecules without intersystem crossing to a long-lived quartet state.7For the two perylene-based molecules,3and 6,the excited state lifetimes of the radical anions are substantially shorter than the excited-state lifetimes of the neutral molecules as expected from the lower energy transitions involved.Contrasting with this behavior are the significantly longer lifetimes of the radical anion excited states of the naphthalene-based molecules,2*5a •-and 2*5b •-,141and 260ps,respectively,compared to the <20ps lifetime of neutral 1*5b .The <50ps lifetime of both 1*2and 1*5b has been attributed to both efficient singlet f triplet intersystem crossing and to very fast internal conversion.42-44The increase in the excited-state lifetimes of radical anions 2*5a •-and 2*5b •-over their neutral counterparts implies that the rates of competitive decay processes,such as intersystem crossing and internal conversion,are slower for the D 1f D 0transition than for the corresponding S 1f S 0transition.The effect of the imide substituent on the radical anion excited-state lifetime was investigated by comparing N ,N ′-bis-(2,5-di-tert -butylphenyl)and N ,N ′-di-n -octyl substituents on pyromellitimide and naphthalene-1,8:4,5-tetracarboxydiimide.Perylene-3,4:9,10-tetracarboxydiimide was not included in the comparison due to the insolubility of its N ,N ′-di-n -octyl deriva-tive.The variation in imide substituent had no effect on the absorption spectra of the neutral molecules nor on their redox properties.Differences were,however,apparent between the spectra of the radical anions and dianions as well as in the lifetimes of the radical anion excited states.A comparison between the ground-state radical anion spectra of 5a •-and 5b •-or between the dianion spectra of 5a 2-and 5b 2-reveals that the lower energy absorption bands are red shifted for the N ,N ′-diaryl-substituted compound relative to the N ,N ′-dialkyl-substituted compound.The D 0f D 1radical anion absorption band occurs at 380cm -1lower energy in 5a •-than in 5b •-,while the S 0f S 1dianion absorption band occurs at 400cm -1lower energy in 5a 2-than in 5b 2-.The lower energy transitions in the N ,N ′-diaryl-substituted reduced diimides suggest that even though the N -phenyl rings are tilted out of the plane of the aromatic diimide as a consequence of steric hindrance between the 2-tert -butyl group and the imide carbonyl groups,there may be enough πoverlap between the N ,N ′-diaryl substituents andthe aromatic diimide to partially delocalize electron density onto the N ,N ′-diaryl substituents.These results are also consistent with N -substitution studies of 1,8-naphthalimides in which it was shown that the fluorescence lifetime was longer and the fluorescence quantum yield was larger for the N-methyl-versus N -phenyl-substituted imide.42,44The excited-state radical anion lifetimes of 2*4a •-vs 2*4b •-and 2*5a •-vs 2*5b •-also show a substituent effect in that the excited-state lifetimes of the N ,N ′-diaryl substituted radical anions are shorter than those of the corresponding N ,N ′-dioctyl compounds,6ps vs 9ps for 2*4a •-and 2*4b •-,respectively,and 140ps vs 260ps for 2*5a •-and 2*5b •-,respectively.The red-shifted radical anion spectra suggest that the D 0-D 1energy gap is smaller in the N ,N ′-diaryl-substituted diimides.As a consequence,the energy gap law 45predicts shorter lifetimes for the N ,N ′-diaryl-substituted diimides.An examination of the data in Table 2shows that the lifetimes of the diimide radical ions are ordered in the following series:4a •-<5a •-=6•-.This is also the order in which 4-6become easier to reduce.As the one-electron reduction potentials for these molecules become more negative,the energies of D 0increase.This may result in a decrease in the D 0-D 1gap,which should decrease the lifetime of 2*R •-.However,this does not take into account the effects of structure on the energy of the D 1state.The measured D 0-D 1energy gaps for 5a •-and 6•-are 12870and 10470cm -1,respectively.Thus,the difference between the observed D 0-D 1gaps for 5a •-and 6•-primarily reflects the difference in their D 1energy levels because both 5a and 6are reduced at approximately the same redox potential.Despite the 2400cm -1difference in the observed D 0-D 1energy gap between 5a and 6,they possess similar radical anion excited-state lifetimes.If predictions of the radical anion excited-state lifetimes based on the energy gap law are valid for the 4-6,the experimental results suggest that the D 0-D 1energy gap for 4•-should be substantially lower in energy than the 10920cm -1value calculated by ZINDO/S.In fact,density functional calculations using the B3LYP method with a 6-31G *basis set predict that the D 0-D 1energy gap for pyromellitic dianhydride is about 8100cm -1.46These same calculations accurately predict the experimentally observed D 0f D 2transition in 4•-near 715nm.Thus,it is likely that the observed ordering of radical anion excited-state lifetimes observed in 4-6is a function of the D 0-D 1energy gap.ConclusionsThe results presented here provide design criteria for electron donor -acceptor systems that use the powerful reducing potential of the radical anion excited states of aromatic imides and diimides and which take advantage of the highly electrochromic nature of the multiple reduced states of these molecules.These constraints mainly involve designing donor -acceptor molecules in which the electronic couplings and free energies of reaction are sufficiently optimized to ensure ultrafast electron transfer from the short-lived radical anion excited states of the aromatic diimides to attached acceptors.This selectivity has already been used in diimide-containing linear and branched donor -acceptor molecules that have demonstrated photonic switching behavior on the basis of electron transfer from radical anion excited states.30,47Also,it has been suggested that photoexcited radical anions may be very useful in studying fundamental aspects of electron transfer.17The radical anions of the diimides in particular are well suited to this task because they are weakly basic relative to quinones and are thus less susceptible to complicating proton transfer reactions.In addition,they can be excited withvisibleFigure 4.Excited-state transient absorption decay kinetics of radical anion of 6in DMF +0.1M Bu 4NPF ser excitation at 715nm was used in both cases.Aromatic Imide and Diimide Radical Anions J.Phys.Chem.A,Vol.104,No.28,20006549light and their highly energetic excited states allow access to electron-transfer reactions that occur in the Marcus inverted region.These highly energetic excited radical anions may also be useful as photoelectrochemical catalysts by acting as electron shuttles.The absorption spectra of the radical anions of the easiest to reduce diimides,5and6,cover much of the solar spectrum.Experiments are currently underway to study photo-induced charge shift reactions involving electrochemically reduced diimides.Experimental SectionReagents.N,N-Dimethylformamide(DMF,Mallinckrodt)and butyronitrile(Mallinckrodt)were purged with N2and stored over molecular sieves prior to use.Tetrabutylammonium hexafluo-rophosphate(Bu4NPF6)was synthesized by metathesis between tetrabutylammonium bromide(Aldrich)and potassium hexaflu-orophosphate(Aldrich)and recrystallized twice from methanol.48 N-(2,5-Di-tert-butylphenyl)-3,4-perylenedicarboximide,493, N,N′-bis-(n-octyl)pyromellitimide,504b,and N,N′-dioctyl-1,8: 4,5-naphthalenetetracarboxydiimide,245b,were synthesized by utilizing published procedures.N,N′-Bis(2,5-di-tert-butylphenyl)-3,4:9,10-perylenetetracarboxydiimide,6,was purchased from Aldrich.The syntheses of N-(2,5-di-tert-butylphenyl)phthalim-ide,1,N-(2,5-di-tert-butylphenyl)-1,8-naphthalimide,2,N,N′-bis(2,5-di-tert-butylphenyl)pyromellitimide,4a,and N,N′-bis-(2,5-di-tert-butylphenyl)-1,8:4,5-naphthalenetetracarboxy-diimide,5a,are presented in the Supporting Information. Electrochemistry.Cyclic voltammetry(CV)and bulk elec-trolysis were carried out using a computer-controlled potentiostat (Princeton Applied Research,model273,M270software package)and a standard three electrode arrangement.CV measurements used both platinum working and auxiliary electrodes and a saturated sodium calomel reference electrode (SSCE).All electrochemical measurements were carried out in N2-purged DMF or butyronitrile with0.1M Bu4NPF6as the supporting electrolyte.The scan rate for CV measurements was typically50-100mV/s.Ferrocene was used as an internal re-dox standard for all potentiometric measurements.Bulk elec-trolyses for anion and dianion ground-state spectra were carried out in an optically transparent thin layer electrochemical cell (OTTLE)51,52utilizing a2cm2,250lines/in.,gold minigrid working electrode.Bulk electrolysis for the transient experiments also utilized the OTTLE.Spectroscopy.Ground-state absorption measurements of neutral and reduced species were recorded using a computer-controlled spectrophotometer(Shimadzu,model1601).Absorp-tion spectra of the electrochemically generated anions and dianions were recorded by passing the light beam from the spectrophotometer through the minigrid electrode,which had an optical density of about0.3.A blank spectrum consisting of the OTTLE filled with solvent and supporting electrolyte was subtracted from each data set.Transient absorption spectra and kinetics of the neutral and electrochemically generated radical anions were recorded using a previously described amplified titanium:sapphire laser sys-tem24,53pumping a tunable optical parametric amplifier(OPA).54 Briefly,the output from a continuous wave,intracavity-doubled Nd:YVO4laser(Spectra Physics Millenia)pumped a self-mode-locked titanium:sapphire oscillator operating at840nm.The 50fs840nm output was temporally stretched,amplified with a regenerative titanium:sapphire amplifier pumped with the output from a frequency-doubled1kHz Nd:YLF(Quantronix, 527DP-S)and then temporally recompressed.The compressed output(150fs)of the amplifier was split with about5%used to make a stable white light continuum probe beam by focusing it into a2mm thick sapphire window.The remaining amplified light was doubled yielding60-100µJ,420nm pulses.The doubled light was used to pump a two stage OPA,which was tunable from475to750nm.Samples were typically excited using0.5µJ focused to ca.200µm.MO Calculations.Molecular orbital calculations were carried out using the semiempirical Hartree-Fock technique with PM3 parametrization within the Hyperchem package(Waterloo, Ontario,Canada).The ground-state structures of the radical anions were calculated using an unrestricted basis set,whereas the dianions structures were calculated using a restricted basis set.The ground-state structures were then subjected to a ZINDO/S CI calculation using163configurations for the dianions and162configurations for the radical anions. Acknowledgment.Work at ANL was supported by the Division of Chemical Sciences,Office of Basic Energy Sciences, Department of Energy,under Contract W-31-109-Eng-38.Work at Northwestern was supported by the National Science Founda-tion(Grant CHE-9732840).Supporting Information Available:Text describing the synthesis and characterization of compounds1,2,4a,and5a. This material is available free of charge via the Internet at http:// .References and Notes(1)Fox,M.A.Chem.Re V.1979,79,253-73.(2)Moutet,J.C.;Reverdy,G.J.Chem.Soc.,mun.1982, 654-5.(3)Shukla,S.S.;Rusling,J.F.J.Phys.Chem.1985,89,3353-8.(4)Eriksen,J.In-situ generated intermediates;Fox,M.A.,Chanon, M.,Eds.;Elsevier:Amsterdam,1988;Vol.Pt.A,pp391-408.(5)Shine,H.J.;Zhao,.Chem.1990,55,4086-9.(6)Legros,B.;Vandereecken,P.;Soumillion,J.P.J.Phys.Chem.1991, 95,5,4752-61.(7)Eggins,B.R.;Robertson,P.K.J.J.Chem.Soc.,Faraday Trans. 1994,90,2249-56.(8)Majima,T.;Fukui,M.;Ishida,A.;Takamuku,S.J.Phys.Chem. 1996,100,8913-19.(9)Tokumura,K.;Mizukami,N.;Udagawa,M.;Itoh,M.J.Phys. Chem.1986,90,3873-3876.(10)Scaiano,J.C.;Johnston,L.J.;McGimpsey,W.G.;Weir,D.Acc. Chem.Res.1988,21,22-9.(11)Tokumura,K.;Ozaki,T.;Udagawa,M.;Itoh,M.J.Phys.Chem. 1989,93,161-164.(12)Samanta,A.;Bhattacharyya,K.;Das,P.K.;Kamat,P.V.;Weir,D.;Hug,G.L.J.Phys.Chem.1989,93,3651-3656.(13)Filatov,I.V.;Chirvonyi,V.S.;Sinyakov,G.N.Opt.Spektrosk. 1994,77,386-8.(14)Breslin,D.T.;Fox,M.A.J.Phys.Chem.1994,98,408-11.(15)Filatov,I.V.;Chirvony,V.S.;Sinyakov,G.N.Proc.SPIE-Int. Soc.Opt.Eng.1995,2370,95-8.(16)Ishida,A.;Fukui,M.;Ogawa,H.;Tojo,S.;Majima,T.;Takamuku, S.J.Phys.Chem.1995,99,10808-14.(17)Cook,A.R.;Curtiss,L.A.;Miller,J.R.J.Am.Chem.Soc.1997, 119,5729-5734.(18)Fujisawa,J.;Ishii,K.;Ohba,Y.;Yamauchi,S.;Fuhs,M.;Mobius, K.J.Phys.Chem.A1999,103,213-216.(19)Ishii,K.;Hirose,Y.;Kobayashi,N.J.Phys.Chem.A1999,103, 1986-1990.(20)Brugman,C.J.M.;Rettschnick,R.P.H.;Hoytink,G.J.Chem. Phys.Lett.1971,8,574-578.(21)Daub,J.;Beck,M.;Knorr,A.;Spreitzer,H.Pure Appl.Chem.1996, 68,1399-1404.(22)Wasielewski,M.R.Chem.Re V.1992,92,435-61.(23)Closs,G.L.;Calcaterra,L.T.;Green,N.J.;Penfield,K.W.;Miller, J.R.J.Phys.Chem.1986,90,3673-3683.(24)Greenfield,S.R.;Svec,W.A.;Gosztola,D.;Wasielewski,M.R. J.Am.Chem.Soc.1996,118,6767-6777.(25)Wiederrecht,G.P.;Niemczyk,M.P.;Svec,W.A.;Wasielewski, M.R.J.Am.Chem.Soc.1996,118,81-8.(26)Osuka,A.;Mataga,N.;Okada,T.Pure Appl.Chem.1997,69,797-802.6550J.Phys.Chem.A,Vol.104,No.28,2000Gosztola et al.。

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Synopsys REFLET 180S Bench 3D (hemispheric) Scatterometer BRDF/BTDFFor 2D/3D scattered light measurements2Complete system delivered in a dark box(Non contractual photography)Synopsys REFLET 180SSynopsys REFLET 180S3DiffuserThe measurements are done in reflection and in transmission.The knowledge of the way light is reflected and transmitted through a diffuser is very important for the use of materials inoptical systems.AluminumReflector materials can have quite complex behaviours depending on the plane of incidence. Synopsys REFLET allows accurate measurements in different planes of incidence (examples:anisotropic material, polarization dependence...).3D ScansDynamic RangeS ynopsys REFLET 180SA compact and motorized optical system for scattering characterization of any kind of materials and objects. It allows you to measure, in a fast and easy way, luminous energy distribution or spectral compositioncontained in the scattering lobes. Consequently, it characterizes surfaces of your examined regions such as roughness, defects as well as types of coatings or paintings… Moreover, the system measures BRDF/BTDF which perfectly represents the way any surface scatters incoming light in 3D space.Polished opticsSpecular surfaces (mirrors), transparent surfaces (glasses, lenses, crystals) have sometimes a very low scattering such as 10-9 sr -1. Those surfaces are very difficult to measure without a high dynamic detection system. Synopsys REFLET has one whichallows measuring BRDF of 10-5 sr -1.©2022 Synopsys, Inc. All rights reserved. Synopsys is a trademark of Synopsys, Inc. in the United States and other countries. A list of Synopsys trademarks is available at /copyright.html . All other names mentioned herein are trademarks or registered trademarks of their respective owners.06/09/22.CS626267225_Light Tec Reflet 180 brochure v2.CosmeticsCosmetic manufacturers need to compare different chemicalmixtures to produce lipsticks or creams. Synopsys REFLET allows the characterization of these types of products on different skins and under different lighting (different spectra).Black MaterialsMainly used in Aerospace applications, black materials and coatings are also difficult to measure without a powerfulinstrument. Those materials need to have a very low BRDF because they absorb a big amount of light: less than 1% of reflection. Synopsys REFLET supports such BSDF level thanks to its high dynamic detection.Illumination Design SoftwareIllumination design software require accurate data to provideaccurate simulations. Synopsys REFLET provides 2D/3D BRDF or BTDF files which can be imported in TRACEPRO, ASAP , LightTools,LucidShape, Photopia or SPEOS.Realistic Rendering SoftwareIn many industries including Automotive, optical designers need to simulate the closest to the reality in order to provide realistic rendering. Today, our Synopsys REFLET Bench allows you to perform the light characterization of headlamps, tail lamps and dashboards. It will also provide you with scattering measurementdata to import into your optical design software.ReferencesADC, Alanod, Alcan, Almeco, Automotive-Lighting, AUO, Arcelor, Bourget, Ball Aerospace, BARCO, Chanel, Dupont, Entire, Essilor, Helbling, Hewlett Packard, Loepfe, STMicroelectronics, Procter & Gamble, PSA, University of Darmstadt, University of Madrid, Volkswagen,…Synopsys’ DesignWare ® Foundation IP , Interface IP , Security IP , and Processor IP are optimized for high performance, low latency, and low power, while supporting advanced processtechnologies from 16-nm to 5-nm FinFET and future process nodes.Synopsys REFLET Software。

吸收光谱简介Absorption Spectrum AnIntroductionWhat is Absorption Spectrum?The absorption spectrum of a material can be defined as the fraction of the incident radiation which is absorbed by that material over a wide range of frequencies. The molecular and atomic composition of a material is used to determine the absorption spectrum. Fundamental radiation is generally observed at those frequencies which get mixed with the energy difference that takes place between two mechanical states of the molecules.The absorption takes place because of the transition between these two states and it is known as the absorption line. The spectrum is composed of several absorption lines. The frequencies where such absorption lines develop along with their relative intensities generally depend on the molecular structure and electronic structure of the sample. The frequencies also depend on molecular interactions. In the sample, the crystal structure is found in solids and on different environmental factors like pressure, temperature, electromagnetic fields, etc.What is Absorption Spectrum?Assingment Experts will explain Absorption Sepctrum in deatils. The absorption spectrum of a material can be defined as the fraction of theincident radiation which is absorbed by that material over a wide range of frequencies. The molecular and atomic composition of a material is used to determine the absorption spectrum. Fundamental radiation is generally observed at those frequencies which get mixed with the energy difference that takes place between two mechanical states of the molecules.The absorption takes place because of the transition between these two states and it is known as the absorption line. The spectrum is composed of several absorption lines. The frequencies where such absorption lines develop along with their relative intensities generally depend on the molecular structure and electronic structure of the sample. The frequencies also depend on molecular interactions. In the sample, the crystal structureis found in solids and on different environmental factors like pressure, temperature, electromagnetic fields, etc.The absorption lines also possess a definite shape and width which are fundamentally determined by the density of states for spectral density of the system. Absorption lines are generally classified by the feature of quantum mechanical change taking place in an atom or molecule. Rotational states sometimes get changed and give result in the development of rotational lines which are found in the region of the microwave spectrum. On the other hand, vibrational lines in correspondence to vibrational state changes in the molecule are found in the area of infrared region. The electronic lines are composed of several changes taking place in the electronic state of a molecule or atom whichare found in the ultraviolet and visible region.It can be noticed that there are various dark lines in the sun’s spectrum. These lines are developed by the atmosphere of the Sun which absorbs light at different wavelengths resulting in different light intensity at the wavelength to appear dark. The molecules and atoms present in a gas absorb certain light wavelengths. The pattern of the lines is very unique with respect to each element which provides us information about the elements which help in making the sun’s atmosphere. The absorption spectra can be observed from spatial regions in the presence of a cooler gas line between in a hotter source and the earth.The absorption spectra can also be observed from the planets with atmospheres, stars, and galaxies. In analyzing the light of the Sun, aspectrometer is used. The spectrometer is a device which separates light by colour and energy. In separating light by colour and energy, the image of the spectrum of the sun gets created. This is quite similar to the absorption spectrum. The dark lines are the areas where the light gets absorbed by different elements present in the Sun’s outer layers. The lowest energy is represented by red light and the highest energy is represented by blue light.The black gaps or lines in the spectrum of the sun are termed as absorption lines. The gas present in the sun’s outer layers develops the absorption lines by absorbing the light. There are different elements such as Helium, hydrogen, carbon, and other smaller quantities of heavy elements in the sun. When the sunlight shines, the elements the energy gets absorbed by the atoms. The atoms can only absorb the lightrelevant to the energy the atoms need. The gaps in the spectrum of the Sun get developed and help in informing the formation of the sun. The emission spectrum is quite different from the absorption spectrum.In developing an absorption spectrum, the light needs to shine through a gas but in creating and emission spectrum a gas needs to be heated up. The atoms present in the gas get absorbed the energy only for a short tenure. The atoms get energetic and jiggled up by heating the gas because of the concentration of a high level of energy. The energy is emitted or re-released as light eventually. Absorption spectrum takes place when the light passes through a dilute and cold gas and characteristic frequencies get absorbed by the atoms present in the gas. The re-emitted light cannot be emitted in a similardirection which is followed by absorbed Photon because of which dark lines in the spectrum are created in the absence of light. The absorption spectrum is the dark lines. The absorption spectrum is defined as an Electromagnetic Spectrum in which the radiation intensity at some specific wavelengths gets decreased. An absorbing substance gets manifested as bands or dark lines. Medically, the absorption spectrum is also defined as an Electromagnetic Spectrum in which radiation intensity at specific ranges of wavelength is manifested as dark lines.X-ray absorptions are highly associated with the excitation taking place in the inner shell electrons in an atom. These changes generally get combined to develop a new absorption line which is typically found in the combined energy develop mainly during the changes. The changes are mainly radiation-vibrationstransitions. The energy which is typically found in the quantum mechanical change fundamentally determines the absorption line frequency. The frequency can get shifted because of several interactions. The magnetic and electric fields can give result in a shift.The interactions with some of the neighbouring molecules can also cause shifts. Absorption lines of any gas-phase molecule can get shifted typically when the molecule is present in either solid or liquid phase and involves in interacting with neighbouring molecules strongly. The shape and width of the absorption lines are generally determined by the observation instrument. The physical environment radiation and material absorbing of that material also determine the shape and width of absorption lines. Now our experts from Instant AssingnmentHelp will tell you about the relationship between Absorption Spectrum andThe relation between Transmission and absorption spectraTransmission and absorption spectra are interconnected. Transmission and absorption spectra are found to represent similar information. Transmission spectrum can be calculated from the absorption spectrum only. Absorption spectrum can also be calculated from transmission spectra. Mathematical transformation is used in calculating either the absorption spectrum or transmission spectrum. It has been observed that a transmission spectrum has maximum intensities where thewavelengths of the absorption spectrum are quite weak because of the transmission of more light through the sample takes place. Similarly, an absorption spectrum is found to have maximum intensities at its wavelengths where the absorption rate is quite stronger.The absorption spectrum is also related to any emission spectrum. Now, it is important to understand the concept of the emission spectrum. The process by which a substance can release energy is known as emission process. The energy which is released from a substance through any emission process can be found in electromagnetic radiation from. Emission can take at any frequency of absorption which makes the absorption lines to gets determined from the emission spectrum. But it is to be remembered that the emissionspectrum will always have different intensity pattern where it becomes distinguished from that of the absorption spectrum. Hence, it can be said that the absorption spectrum and emission spectrum can never be equivalent. The emission spectrum can be used to calculate the absorption spectrum with the application of effective theoretical models and other relevant information from where quantum mechanical states of a substance can be understood.Relationship between Absorption spectrum and reflection and scattering spectraThe absorption spectrum is also related to reflection and scattering spectra. The scattering and reflection spectra of any material getinfluenced by the absorption spectrum and index of refraction of that material. Extinction coefficient quantifies the absorption spectrum and index coefficients along with extinction coefficients which are related through Kramers-Kroening relation quantitatively. Therefore, it can be said that reflection or scattering spectrum standardize absorption spectrum can give rise to absorption spectrum.Reflection or scattering spectrum assumptions or models need to be simplified so that it can lead to effect an approximation of the derivation of absorption spectra. In the domain of chemical analysis, we can find the use of absorption spectroscopy because of the quantitative nature and specificity of the absorption spectrum. The specificity enables the compounds to get distinguished from each other in a mixture whichmakes absorption spectroscopy to be highly useful in different applications. For example, the presence of any pollutant in the air can be identified by the use of infrared gas analyzers.These analyses are also used to distinguish the air pollutant from oxygen, water, nitrogen, and other constituents. The specificity is also helpful in allowing several unknown samples to get rightly identified. It can be done by comparing the measured spectrum with the findings of reference spectra. It has been found that qualitative information of any sample can also be determined even if the information is not present in a library. For example, infrared spectra have several characteristics absorption bands which help in indicating the presence of carbon-oxygen bond or Carbon hydrogen bonds.Absorption spectrum can also be related to the quantity of material present with the use of Beer-Lambert law. This relationship is established quantitatively. In determining the typical compound concentration, it needs knowledge of the absorption coefficient of the compound. The absorption coefficient can be known from several reference sources and can be measured by accessing calibre standard spectrum with an available target concentrationabsorption spectrumAbsorption spectroscopy and its applicationAbsorption spectroscopy is one of the methods with the help of which a substance can get characterized by the support of wavelengths at which the spectrum of colour gets absorbedduring the passage of light through a substance solution. It is one of the fundamentally used methods used in assessing the chromospheres concentrations in the solutions. Absorption spectroscopy can also be explained as a non-destructive technique which is widely used by biochemists and biologists to assess the characteristic parameters and cellular components of functional molecules.This quantification is highly important in the domain of systems biology. In developing metabolic pathway quantitative depiction, various variables and parameters are needed which are to be assessed experimentally. Ultraviolet-visible absorption spectroscopy is used in producing experimental data which help in modelling techniques of system biology. These techniques use kinetic parameters andconcentrations of enzymes of signalling on metabolic pathways, fluxes, and intercellular metabolic concentrations. Absorption spectroscopy also describes the usage of the technique in quantifying bio-molecules and investigating bio-molecular interactions.Absorption spectroscopy is a significant technique which is used in chemistry to study simple inorganic species. It refers to spectroscopic techniques which are used in measuring radiation absorption as a function of wavelength or frequency when the interaction between absorption radiation and sample takes place. Photons are absorbed by the samples from the field of radiation. The absorption intensity varies as a frequency function and this absorption intensity is the absorption spectrum. Absorption spectroscopy is fundamentallyperformed across an absorption spectrum or electromagnetic spectrum.In the domain of analytical chemistry, absorption spectroscopy is used to assess the presence of any specific substance in a sample. In several cases, absorption spectroscopy is also used to quantify the quantity of a substance. In the domain of analytical applications, ultraviolet-visible and infrared spectroscopy is commonly observed. In the study of atomic physics, remote sensing, molecular physics, and astronomical spectroscopy, the use of absorption spectroscopy are widely observed.There are various experimental approaches which are used to measure the absorption spectrum. The most commonly used arrangement is to guide the regeneratedradiation beam at the sample in detecting the radiation intensity passing through it. The transmitted energy can be applied in calculating the absorption. The sample arrangement source and detection technique are also very used quite significantly depending on the objective of the experiment and that of the frequency range.Advantages of absorption spectroscopyThere can be several advantages of absorption spectroscopy because it can be used as an analytical method where measurements can be accomplished without any contact between the sample and the instrument. Radiation which travels between an instrument and a sample contains some important spectral information and measurement which is done remotely. Remote spectral sensing is quite significant indifferent situations. For example, hazardous and toxic environments can be measured without risking any instrument or operator.The material of the sample needs not to be brought into direct contact with any instrument which can prevent cross-contamination at a possible rate. Remote spectral measurements have certain challenges as compared to that of the laboratory measurements. To reduce such challenges, differential optical absorption spectroscopy has become quite popular because it mainly emphasizes on the features of differential absorption and erasers broadband absorption like the extinction of aerosol extinction because of Rayleigh scattering. This technique is used in airborne, ground-based, and satellite-based measuring actions. There are certain ground-based techniques whichprofile the possibilities of retrieving stratospheric and tropospheric trace gas profiles.The absorption lines also possess a definite shape and width which are fundamentally determined by the density of states for spectral density of the system. Absorption lines are generally classified by the feature of quantum mechanical change taking place in an atom or molecule. Rotational states sometimes get changed and give result in the development of rotational lines which are found in the region of the microwave spectrum. On the other hand, vibrational lines in correspondence to vibrational state changes in the molecule are found in the area of infrared region. The electronic lines are composed of several changes taking place in the electronic state of a molecule or atom which are found in the ultraviolet and visible region.Itcan be noticed that there are various dark lines in the sun’s spectrum. These lines are developed by the atmosphere of the Sun which absorbs light at different wavelengths resulting in different light intensity at the wavelength to appear dark. The molecules and atoms present in a gas absorb certain light wavelengths. The pattern of the lines is very unique with respect to each element which provides us information about the elements which help in making the sun’s atmosphere. The absorption spectra can be observed from spatial regions in the presence of a cooler gas line between in a hotter source and the earth.The absorption spectra can also be observed from the planets with atmospheres, stars, and galaxies. In analyzing the light of the Sun, a spectrometer is used. The spectrometer is adevice which separates light by colour and energy. In separating light by colour and energy, the image of the spectrum of the sun gets created. This is quite similar to the absorption spectrum. The dark lines are the areas where the light gets absorbed by different elements present in the Sun’s outer layers. The lowest energy is represented by red light and the highest energy is represented by blue light.The black gaps or lines in the spectrum of the sun are termed as absorption lines. The gas present in the sun’s outer layers develops the absorption lines by absorbing the light. There are different elements such as Helium, hydrogen, carbon, and other smaller quantities of heavy elements in the sun. When the sunlight shines, the elements the energy gets absorbed by the atoms. The atoms can only absorb the light relevant to the energy the atoms need. The gapsin the spectrum of the Sun get developed and help in informing the formation of the sun. The emission spectrum is quite different from the absorption spectrum.In developing an absorption spectrum, the light needs to shine through a gas but in creating and emission spectrum a gas needs to be heated up. The atoms present in the gas get absorbed the energy only for a short tenure. The atoms get energetic and jiggled up by heating the gas because of the concentration of a high level of energy. The energy is emitted or re-released as light eventually. Absorption spectrum takes place when the light passes through a dilute and cold gas and characteristic frequencies get absorbed by the atoms present in the gas. The re-emitted light cannot be emitted in a similar direction which is followed by absorbed Photonbecause of which dark lines in the spectrum are created in the absence of light. The absorption spectrum is the dark lines. The absorption spectrum is defined as an Electromagnetic Spectrum in which the radiation intensity at some specific wavelengths gets decreased. An absorbing substance gets manifested as bands or dark lines. Medically, the absorption spectrum is also defined as an Electromagnetic Spectrum in which radiation intensity at specific ranges of wavelength is manifested as dark lines.X-ray absorptions are highly associated with the excitation taking place in the inner shell electrons in an atom. These changes generally get combined to develop a new absorption line which is typically found in the combined energy develop mainly during the changes. The changes are mainly radiation-vibrations transitions. The energy which is typically foundin the quantum mechanical change fundamentally determines the absorption line frequency. The frequency can get shifted because of several interactions. The magnetic and electric fields can give result in a shift.The interactions with some of the neighbouring molecules can also cause shifts. Absorption lines of any gas-phase molecule can get shifted typically when the molecule is present in either solid or liquid phase and involves in interacting with neighbouring molecules strongly. The shape and width of the absorption lines are generally determined by the observation instrument. The physical environment radiation and material absorbing of that material also determine the shape and width of absorption lines. Now our experts from Instant AssingnmentHelp will tell you about the relationship between Absorption Spectrum andThe relation between Transmission and absorption spectraTransmission and absorption spectra are interconnected. Transmission and absorption spectra are found to represent similar information. Transmission spectrum can be calculated from the absorption spectrum only. Absorption spectrum can also be calculated from transmission spectra. Mathematical transformation is used in calculating either the absorption spectrum or transmission spectrum. It has been observed that a transmission spectrum has maximum intensities where thewavelengths of the absorption spectrum are quite weak because of the transmission of more light through the sample takes place. Similarly, an absorption spectrum is found to have maximum intensities at its wavelengths where the absorption rate is quite stronger.The absorption spectrum is also related to any emission spectrum. Now, it is important to understand the concept of the emission spectrum. The process by which a substance can release energy is known as emission process. The energy which is released from a substance through any emission process can be found in electromagnetic radiation from. Emission can take at any frequency of absorption which makes the absorption lines to gets determined from the emission spectrum. But it is to be remembered that the emissionspectrum will always have different intensity pattern where it becomes distinguished from that of the absorption spectrum. Hence, it can be said that the absorption spectrum and emission spectrum can never be equivalent. The emission spectrum can be used to calculate the absorption spectrum with the application of effective theoretical models and other relevant information from where quantum mechanical states of a substance can be understood.Relationship between Absorption spectrum and reflection and scattering spectraThe absorption spectrum is also related to reflection and scattering spectra. The scattering and reflection spectra of any material getinfluenced by the absorption spectrum and index of refraction of that material. Extinction coefficient quantifies the absorption spectrum and index coefficients along with extinction coefficients which are related through Kramers-Kroening relation quantitatively. Therefore, it can be said that reflection or scattering spectrum standardize absorption spectrum can give rise to absorption spectrum.Reflection or scattering spectrum assumptions or models need to be simplified so that it can lead to effect an approximation of the derivation of absorption spectra. In the domain of chemical analysis, we can find the use of absorption spectroscopy because of the quantitative nature and specificity of the absorption spectrum. The specificity enables the compounds to get distinguished from each other in a mixture whichmakes absorption spectroscopy to be highly useful in different applications. For example, the presence of any pollutant in the air can be identified by the use of infrared gas analyzers.These analyses are also used to distinguish the air pollutant from oxygen, water, nitrogen, and other constituents. The specificity is also helpful in allowing several unknown samples to get rightly identified. It can be done by comparing the measured spectrum with the findings of reference spectra. It has been found that qualitative information of any sample can also be determined even if the information is not present in a library. For example, infrared spectra have several characteristics absorption bands which help in indicating the presence of carbon-oxygen bond or Carbon hydrogen bonds.Absorption spectrum can also be related to the quantity of material present with the use of Beer-Lambert law. This relationship is established quantitatively. In determining the typical compound concentration, it needs knowledge of the absorption coefficient of the compound. The absorption coefficient can be known from several reference sources and can be measured by accessing calibre standard spectrum with an available target concentrationabsorption spectrumAbsorption spectroscopy and its applicationAbsorption spectroscopy is one of the methods with the help of which a substance can get characterized by the support of wavelengths at which the spectrum of colour gets absorbed during the passage of light through a substancesolution. It is one of the fundamentally used methods used in assessing the chromospheres concentrations in the solutions. Absorption spectroscopy can also be explained as a non-destructive technique which is widely used by biochemists and biologists to assess the characteristic parameters and cellular components of functional molecules.This quantification is highly important in the domain of systems biology. In developing metabolic pathway quantitative depiction, various variables and parameters are needed which are to be assessed experimentally. Ultraviolet-visible absorption spectroscopy is used in producing experimental data which help in modelling techniques of system biology. These techniques use kinetic parameters and concentrations of enzymes of signalling onmetabolic pathways, fluxes, and intercellular metabolic concentrations. Absorption spectroscopy also describes the usage of the technique in quantifying bio-molecules and investigating bio-molecular interactions.Absorption spectroscopy is a significant technique which is used in chemistry to study simple inorganic species. It refers to spectroscopic techniques which are used in measuring radiation absorption as a function of wavelength or frequency when the interaction between absorption radiation and sample takes place. Photons are absorbed by the samples from the field of radiation. The absorption intensity varies as a frequency function and this absorption intensity is the absorption spectrum. Absorption spectroscopy is fundamentallyperformed across an absorption spectrum or electromagnetic spectrum.In the domain of analytical chemistry, absorption spectroscopy is used to assess the presence of any specific substance in a sample. In several cases, absorption spectroscopy is also used to quantify the quantity of a substance. In the domain of analytical applications, ultraviolet-visible and infrared spectroscopy is commonly observed. In the study of atomic physics, remote sensing, molecular physics, and astronomical spectroscopy, the use of absorption spectroscopy are widely observed.There are various experimental approaches which are used to measure the absorption spectrum. The most commonly used arrangement is to guide the regeneratedradiation beam at the sample in detecting the radiation intensity passing through it. The transmitted energy can be applied in calculating the absorption. The sample arrangement source and detection technique are also very used quite significantly depending on the objective of the experiment and that of the frequency range.Advantages of absorption spectroscopyThere can be several advantages of absorption spectroscopy because it can be used as an analytical method where measurements can be accomplished without any contact between the sample and the instrument. Radiation which travels between an instrument and a sample contains some important spectral information and measurement which is done remotely. Remote spectral sensing is quite significant indifferent situations. For example, hazardous and toxic environments can be measured without risking any instrument or operator.The material of the sample needs not to be brought into direct contact with any instrument which can prevent cross-contamination at a possible rate. Remote spectral measurements have certain challenges as compared to that of the laboratory measurements. To reduce such challenges, differential optical absorption spectroscopy has become quite popular because it mainly emphasizes on the features of differential absorption and erasers broadband absorption like the extinction of aerosol extinction because of Rayleigh scattering. This technique is used in airborne, ground-based, and satellite-based measuring actions. There are certain ground-based techniques which。

光谱特征英文Spectral FeaturesSpectral features refer to the unique characteristics of the electromagnetic spectrum that are associated with different materials, substances, or objects. These features are determined by the way in which the material interacts with and absorbs or reflects different wavelengths of light. Spectral features can be used to identify and analyze various substances, including chemicals, minerals, and biological materials, through techniques such as spectroscopy.One of the most important spectral features is the absorption spectrum, which represents the wavelengths of light that a material absorbs. Each material has a unique absorption spectrum, which is determined by the molecular structure and composition of the material. The absorption spectrum can be used to identify the presence of specific elements or compounds in a sample, as well as to quantify their concentrations.Another important spectral feature is the emission spectrum, which represents the wavelengths of light that a material emits. When a material is excited, such as by heat or electricity, it can release energy in the form of photons, which have specific wavelengths. The emission spectrum of a material can be used to identify the presence of specific elements or compounds, as well as to study the energy levels and transitions within the material.Reflectance spectra are also important spectral features, as they represent the wavelengths of light that a material reflects. The reflectance spectrum of a material can beused to study the surface properties of the material, aswell as to identify the presence of specific materials or coatings.Spectral features can also be used to study thestructure and composition of materials at the molecular level. For example, the vibrational and rotational spectraof molecules can be used to identify the presence ofspecific functional groups or to study the interactions between molecules.In addition to identifying and analyzing materials, spectral features can also be used in a wide range of applications, such as remote sensing, environmental monitoring, and medical diagnostics. For example,satellite-based remote sensing can use spectral features to map and monitor the Earth's surface, while medical imaging techniques like magnetic resonance imaging (MRI) and positron emission tomography (PET) rely on the unique spectral properties of different tissues and materials within the body.Overall, spectral features are a fundamental aspect of the physical world, and their study and analysis have ledto numerous scientific and technological advancements across a wide range of fields.光谱特征光谱特征指的是与不同材料、物质或物体相关的电磁光谱的独特特征。

光谱带宽英文The spectral bandwidth is a measure of the range of frequencies or wavelengths within a given spectrum. It is typically defined as the difference between the highest and lowest frequencies or wavelengths present in the signal. In the context of optics and spectroscopy, the spectral bandwidth refers to the range of frequencies or wavelengths over which a detector or system is sensitive.There are different ways to quantify the spectral bandwidth depending on the specific application. In spectroscopy, the full width at half maximum (FWHM) is commonly used to measure the spectral bandwidth of a peak. This measure represents the width of the peak at half ofits maximum intensity and provides a standardized way to compare the bandwidths of different spectral lines.In telecommunications, the spectral bandwidth of asignal is often expressed in terms of the data rate or bandwidth required to transmit the signal. This is important for determining the capacity of a communication channel and ensuring that the signal can be accurately and efficiently transmitted.In general, a wider spectral bandwidth allows for the transmission of more information or the detection of a broader range of signals. However, a wider bandwidth also requires more resources and may lead to increased noise or interference. Therefore, there is often a trade-off between spectral bandwidth and signal quality in many applications.在光谱学中，光谱带宽是指信号中包含的频率或波长范围的度量。