Showing papers on "Absorption band published in 1985"
TL;DR: In this article, the temperature dependence of electron transfer to ubiquinone from the bacteriopheophytin (BPh) that serves as an initial electron acceptor (I) in reaction centers of Rhodopseudomonas sphaeroides was examined.
223 citations
TL;DR: In this paper, a series of crystals with different magnesium-doping levels and Li/Nb ratios were investigated, and the defects were introduced either by x-ray irradiation at low temperatures (10−85 K) or by reduction at high temperature in a vacuum.
Abstract: Optical absorption, electron spin resonance (ESR), thermoluminescence, and x‐ray‐induced luminescence techniques have been used to characterize point defects in LiNbO3. A series of crystals with different magnesium‐doping levels and Li/Nb ratios were investigated, and the defects were introduced either by x‐ray irradiation at low temperatures (10–85 K) or by reduction at high temperature in a vacuum. The samples may be classified into two groups, according to their response to radiation and reduction. A threshold (i.e., a sharp change in behavior due to a small change in composition) marks the change from one type of response to the other. The concentrations of both magnesium and lithium affect the threshold level. An electron trap, represented by an optical absorption band peaking at 1200 nm and a broad ESR spectrum centered at gc=1.82, is observed in several of the heavily‐doped crystals after irradiation. A corresponding hole trap produced during the same irradiation has an optical absorption peak near...
138 citations
TL;DR: In this paper, LiNbO3 has been shown to have a high photoconductivity, which is related to a distinctive electronic environment for impurities in the damage-resistant crystals.
Abstract: Compositions of lithium niobate containing 4.5 at.% or more MgO have the ability to transmit, without distortion, light 100 times as intense as undopecl compositions. Holographic diffraction measurements of photorefraction have demonstrated that the improved performance is due to a hundredfold increase in the photoconductivity, rather than to a decrease in the Glass current. The damage-resistant compositions are also distinguished by a thermal activation energy of 0.1 eV for the diffraction efficiency, an OH-stretch vibration at 2.83 Am, a lattice phonon absorption at 21.2 Am, an electron spin resonance signal for Fe impurities at 1500 G, and, after reduction by heating in a vacuum, an optical absorption band at 1.2 um. (The corresponding values for undopedl LiNbO3 are 0.5 eV, 2.87 um, 21.8 um, 790 G, and 0.5 um, respectively.) The high photoconductivity is thus related to a distinctive electronic environment for impurities in the damage-resistant crystals. The photoconductivity strongly affects the impedance and time constants of signal processing devices made of LiNbO3.
104 citations
TL;DR: A series of glass specimens was prepared from TeO2 glass and from the binary tungsten tellurite glasses (TeO2-WO3) and their densities, optical absorption edges and infrared absorption spectra were measured.
Abstract: A series of glass specimens was prepared from TeO2 glass and from the binary tungsten tellurite glasses (TeO2-WO3) and their densities, optical absorption edges and infrared absorption spectra were measured. It was found that the fundamental absorption edge is a function of glass composition, and absorption in this region is due to indirect electronic transitions in k-space. The main infrared absorption bands in the TeO2-WO3 glasses are related to those characteristics of the TeO2 component.
94 citations
TL;DR: Etude experimentale etat a etat par fluorescence induite par laser et comparaison aux calculs ainsi que laissez-au-sous-vous quantification de l’efficacité de la fluorescence d’universitaire olympique.
Abstract: A complete characterization of rotational and electronic fine-structure-state distributions of the product OH from photodissociation of ${\mathrm{H}}_{2}$O in the first absorption band is presented. Vibrationally excited water molecules are prepared in a well-defined rotational state by ir excitation, and photodissociation of this state is studied. The theory is based on numerically exact wave functions for ground-state water; the dissociative wave function is expanded in terms of $\mathrm{OH}(^{2}\ensuremath{\Pi})$ wave functions (including electronic structure) and inelastic effects in the excited state are shown to be negligible. The comparison between theory and experiment is quantitative on the basis of six quantum numbers.
89 citations
TL;DR: In this article, the infrared absorption spectra of the vitreous Co3O4-P2O5 system have been measured in the frequency region 4000 to 200 cm−1.
Abstract: The infrared absorption spectra of the vitreous Co3O4-P2O5 system have been measured in the frequency region 4000 to 200 cm−1. Absorption bands and mode attributions have been fully discussed. Absorption frequencies and intensities are found to be strongly and systematically dependent on glass composition. On this basis it is found that this glass system can be divided into three distinct “compositional regions”. Similar “three region” behaviour is reported for the compositional dependence of density and molar volume of mixing of Co3O4-P2O5 glass. Quantitative justification for the band attributions has been attempted.
71 citations
TL;DR: In this article, it was recognized that derivative spectrophotometry, introduced about three decades ago, can be a very useful analytical tool for characterizing an analyte band that is overlapped by other absorption bands with different halfwidths.
Abstract: Absorption and emission spectroscopy in the ultraviolet and visible regions, apart from being the earliest physical techniques of analysis, have great utility in solving a variety of structural and analytical problems [l-41. However, in many cases the quantitative determination of individual components in a mixture by UV-VIS spectroscopy becomes very difficult owing to the spectral similarities and overlapping of weak absorption bands of one component by strong absorption bands of other components. It was recently recognized that derivative spectrophotometry, introduced about three decades ago [5-81 and originally proposed by Rutherford [9], can be a very useful analytical tool for characterizing an analyte band that is overlapped by other absorption bands with different halfwidths. On differentiation, the intensity of the absorption band with a small halfwidth increases more than that of a band with a large halfwidth [10]. The central idea behind the development of the science of derivatized spe...
71 citations
70 citations
TL;DR: In this article, the long wavelength tail of the S1 absorption band of a probe molecule is monitored on a picosecond time scale, which is used to study energy transfer from the solvent to the probe molecule and vice versa.
Abstract: Energy is supplied to the solvent or solute molecules via resonantly absorbed infrared photons. The long wavelength tail of the S1 absorption band of a probe molecule is monitored on a picosecond time scale. This technique is used to study energy transfer from the solvent to the probe molecule and vice versa. Exciting a vibrational mode of the probe molecules, the energy is rapidly redistributed via intramolecular processes followed by an intermolecular dissipation to the solvent with time constants of ∼10 ps. Intermolecular energy transfer from the solvent to the probe molecules is observed within ≲5 ps, independent of the solvent.
66 citations
TL;DR: In this paper, the distribution and valance state of titanium ions were performed by x-ray techniques and laser Raman microprobe methods, and the presence of other impurity ions, specifically iron, was also determined.
Abstract: The process of growing large diameter single crystals of Al2O3:Ti3+ by vertical solidification of the melt is described, and some of the problems in producing high‐optical quality material are discussed. The characterization of the distribution and valance state of titanium ions was performed by x‐ray techniques and laser Raman microprobe methods. The presence of other impurity ions, specifically iron, was also determined. In some cases titanium was found in the grown crystal to be in the rutile form. In addition, Ti‐Fe pairs, and concentrated regions of titanium on the surface of the boule were also observed. Some procedures for minimizing these problems are discussed. The results of optical absorption, fluorescence, and lifetime measurements are reported. The addition of Fe is shown to produce a broad absorption band in the red region of the spectrum, and two‐photon laser excitation terminating in the ultraviolet spectral region produces a broad blue emission band.
61 citations
TL;DR: In this paper, an electrochromic band shift of the chlorophyll a absorption band was detected in the 650-714 nm range, and the oscillation pattern 0:0:+:+ corresponds to those at 514 nm, supporting the former conclusion that the states S2 and S3 have a surplus charge compared to S0 and S1.
TL;DR: In this paper, a detailed investigation of rotationally inelastic effects in photodissociation of water in the first absorption band using a recently calculated ab initio potential energy surface of the A 1B1 state was performed.
Abstract: We report a detailed investigation of rotationally inelastic effects in the photodissociation of water in the first absorption band using a recently calculated ab initio potential energy surface of the A 1B1 state. Although the excited state potential anisotropy is large it has only very weak influence on the rotational state distributions which thus simply reflect the angular behavior of the ground state wave function of the parent molecule. The reason is that both potential energy surfaces have roughly the same equilibrium angle. Strong inelastic effects are observed, however, for dissociation out of excited bent states because the corresponding ground state wave function extends over a considerably wider angular range and thus the more anisotropic regions of the excited state potential are probed. Calculations are performed on three levels of accuracy for the continuum wave function: close‐coupling, coupled‐states (CS), and infinite‐order‐sudden (IOS) approximation. The ground state wave function is treated numerically exactly. The CS approximation is found to be extremely reliable for those cases studied in this work. The accuracy of the IOS approximation depends very much on the region of orientation angle probed by the ground state and therefore a general conclusion is not possible. Finally, OH rotational state distributions obtained from the dissociation of water and from H–OH scattering at equivalent translational energies are compared and found to be extremely different.
TL;DR: Constraints on the possible structural changes that can be invoked to explain the spectral shifts induced in the acid and deionized species are provided.
TL;DR: In this article, the changes in the optical characteristics of pulse radiolytically generated electrons have been measured in LiCl solutions in H/sub 2/O and D/sub O at 21 /sup 0/C over the range 0-15 M.
Abstract: The changes in the optical characteristics of pulse radiolytically generated electrons have been measured in LiCl solutions in H/sub 2/O and D/sub 2/O at 21 /sup 0/C over the range 0-15 M. Increasing the LiCl concentration causes a nonuniform increase of the energy of the e/sub aq//sup -/ absorption spectrum maximum and the half-width of the absorption band. More rapid changes in concentration regions corresponding to LiCl. 6H/sub 2/O and LiCl. 4H/sub 2/O are related to solution microstructure. The shift of the e/sub aq//sup -/ absorption spectrum is compared with the experimentally measured displacement of the e/sub aq//sup -/ conduction band. The latter, as well as changes of the electron hydration energy, is found to be responsible for the observed differences in the e/sub aq//sup -/ absorption band with increasing LiCl concentration. Spectral characteristics are analyzed from the positions of trap-trap and continuum concepts of optical excitation and from cavity and hydrated H/sub 2/O/sup -/ electron models. 29 references, 4 figures.
TL;DR: In this article, the ground and lowest excited singlet states of styrene were analyzed using an extended PPP-CI model and the Franck-Condon factors calculated from the model were used to analyze the intensity distribution of the ultraviolet absorption bands of the jet-cooled molecule from 34,000 to 46,000 cm−1.
Abstract: Vibrational analyses of the ground and lowest excited singlet states of styrene are performed using an extended PPP‐CI model. Franck–Condon factors calculated from the model are used to analyze the intensity distribution of the ultraviolet absorption bands of the jet‐cooled molecule from 34 000–46 000 cm−1. For the weak first absorption system (S1←S0) the small amount of vibrational excitation found experimentally is well described by the theoretical model. The relatively intense second absorption band shows more extended vibrational development. The model predicts that two electronic transitions S2←S0 and S3←S0 contribute to the absorption spectrum in this region and that a large number of vibrational excitations involving carbon–carbon stretching motions are active. For the S1←S0 and S2←S0 transitions a refinement of the theoretical model is performed to calculate the excited state equilibrium geometries from the measured spectra. Because of the large number of vibrations and the evidence for mixing amo...
TL;DR: In this article, it is suggested that a high concentration of microscopic and macroscopic defects, not observed in clusters grown with other techniques, is probably responsible for the behavior of gold particles sputtering at different substrate temperatures.
Abstract: Gold particles, sputtered at different substrate temperatures, have been analyzed by both optical absorption and transmission electron microscopy techniques. Changes in the absorption band depending on the preparation of the films was observed and related to the bulk properties of the material. However, the bandwidth was nearly independent of particle concentration. It is suggested that a high concentration of microscopic and macroscopic defects, not observed in clusters grown with other techniques, is probably responsible for this behavior.
01 Jan 1985
TL;DR: Ootical rotary dispersion (ORD) and circular dichroism (CD) as discussed by the authors are two interrelated modes of the optical activity spectrum, and they are interconvertible by a well-established mathematical transformation.
Abstract: Publisher Summary Optical activity spectroscopy is a recognized tool for the examination of the conformation of biological macromolecules. This chapter discusses Ootical rotary dispersion (ORD) and circular dichroism (CD). They are two interrelated modes of the optical activity spectrum. ORD is the wavelength dependence of the ability of a chromophore to rotate a plane of linearly polarized light. The spectrum from a single transition is composed of a positive and a negative component, and has finite optical activity throughout the entire spectrum except at the wavelength of the transition. CD, on the other hand, is the wavelength dependence of the difference in the ability of the chromophore to absorb right- and left-handed circularly polarized light. The nature of the spectrum is that of an absoption band in solution, but the band could be either positive or negative. This absorption-dispersion profile of the optical activity spectrum is called a Cotton effect. ORD and CD profiles are interconvertible by a well-established mathematical transformation. CD spectroscopy has been the more prevalently used mode of optical activity spectroscopy because of the simplification of the spectrum resulting from its property of vanishing in all other areas of the spectrum except within the region of an optically active absorption band
TL;DR: In this article, a color-center laser was used to irradiate solid argon containing 1% of 13 C 18 O (C 18 O), whose frequency was coincident with the first overtone absorption band of CO. This emission consists of an intense complex system between 650 and 800 nm and a weaker single progression extending from 320 to 640 nm.
TL;DR: In this paper, preliminary results for the photodissociation of water within the first absorption band obtained from approximate 3D quantal calculations using an ab initio potential energy surface for the A 1 B 1 state without adjustable parameters.
TL;DR: In this paper, the average angle between the ground state BPh Q y transitions and the 890 nm transition is approx. 50° with the dimer absorption band, and the polarization ratio of the light-induced absorption decrease at 815 nm is not consistent with that decrease being due solely to an electrochromic bandshift of the 813 nm transition.
TL;DR: In this article, an optical absorption technique was used to study the irradiation defects in lithium oxide, irradiated by oxygen ions with energies of 0.5, 0.75, 1.25 and 100 MeV.
TL;DR: In this article, the ground and excited singlet and triplet states of 9,10-anthraquinone and its 1,4-dihydroxy and 1, 4-diamino derivatives are investigated by ab initio configuration interaction calculations, using a floating Gaussian basis.
Abstract: The ground and excited singlet and triplet states of 9,10-anthraquinone and its 1,4-dihydroxy and 1,4-diamino derivatives are investigated by ab initio configuration interaction calculations, using a floating Gaussian basis. For anthraquinone the calculated electronic absorption spectrum is consistent with previous experimental and theoretical results. The possible mechanisms of intersystem crossing and intensity borrowing in phosphorescence are discussed in terms of first- and second-order spin-orbit and vibronic perturbations of the computed singlet and triplet states. The calculated spectra of the 1,4-disubstituted derivatives are more complex than previously suggested from low-resolution polarized absorption studies. The principal effect of 1,4-substitution by electron donating groups is shown to be a powerful conjugative effect which significantly modifies selected molecular orbitals of anthraquinone; the resultant effect on the absorption spectra is the creation of two new substituent-induced π π* transitions, one of which corresponds to the intense visible absorption band of these systems.
TL;DR: In this article, the authors investigated the optical absorption and luminescence spectra of 6-methyl merocyanine diluted with arachidic acid at room temperature, and showed that the exciton-phonon interaction is weak and two-dimensional in the chromophore aggregates.
TL;DR: In this paper, the vibrational modes of disilver in rare-gas matrices are characterized by resonance Raman scattering and the trap sites are identified as localized or resonant modes of the molecule.
TL;DR: In this article, the first absorption band at 38.5 × 103 cm-1(Iµ= 300 mol-1 dm3 cm-3 cm−1) is assigned to the 1B2→1A1(or 1Lb→1a) transition, which corresponds to that of 1B 2u→1G in benzene.
Abstract: Assignments of the u.v. absorption and intramolecular charge-transfer (c.t.) emission in phenylpentamethyldisilane have been studied by measurements of m.c.d. spectra and fluorescence polarization spectra with the aid of CNDO/S calculations. From the m.c.d. spectra the first absorption band at 38.5 × 103 cm–1(Iµ= 300 mol–1 dm3 cm–1) is assigned to the 1B2→1A1(or 1Lb→1A) transition, which corresponds to that of 1B2u→1A1g in benzene. Using m.c.d. measurements and molecular-orbital calculations, the mechanism of charge migration from the phenyl ring to the disilanyl group in the first excited state is established. On the basis of fluorescence polarization, in addition to the m.c.d. results, the c.t. emission of phenyldisilane is ascribed to that from the 1(2pπ, 3dπ) c.t. state produced by the 2pπ* orbital (the phenyl ring) to the vacant 3dπ orbital (the Si—Si bond) intramolecular charge-transfer transition.
TL;DR: In this paper, a luminescent garnet, called CALGAR (Ca3Al2Ge3O12), is used for ionic transference and electrical conductivity measurement.
Abstract: Electrical conductivity and ionic transference measurements performed at varying temperatures and partial pressures of oxygen show that CALGAR (Ca3Al2Ge3O12), a luminescent garnet, is a mixed ionic‐electronic conductor. An activation energy of 1 eV for ionic diffusion is measured. An absorption band at 400 nm, whose magnitude can be controlled by varying the annealing atmosphere, is attributed to an O− center.
TL;DR: In this article, high density of BH pair was produced by interaction between atomic hydrogen and boron in B-diffused silicon, and the absorption band at 1873cm-1 was first observed using FT-IR spectroscopy.
TL;DR: In this paper, the authors measured the emission and excitation spectra of the phosphor CsI: Tl+ with respect to the adiabatic potential energy surface and showed that the presence of three distinct sets of minima on the energy surface represents the relaxed excited A state.
Abstract: Emission and excitation spectra of the phosphor CsI: Tl+ have been measured between 4·2 K and room temperature. Quenched crystals of CsI: Tl+, when excited in any of the five absorption bands that lie between 290 and 238 nm, exhibit two overlapping luminescence bands that lie at 2·19 eV (560 nm) and 2·53 eV (490 nm) at 4·2 K. A third emission band at 3·08eV (405 nm) is excited only on the long-wavelength side of the first absorption band. Peak excitation efficiency at 4·2 K is at 290 nm, whereas for the 2·19 eV principal emission it is at 280 nm. A fourth emission band at 1·78 eV (700 nm) is observed only in unquenched crystals and is therefore probably associated with (Tl+)2 dimers. The presence of three distinct emission bands which are all excited in the first (A) absorption band is a most unusual occurrence in this type of phosphor, but it is concluded that the presence of three distinct sets of minima on the adiabatic potential energy surface representing the relaxed excited A state is theor...
TL;DR: In this article, an extremely sensitive method to investigate nonradiative processes following optical excitation was described, where the absorbed energy which is converted into phonons leads to a measurable increase of the sample temperature.
Abstract: We describe an extremely sensitive method to investigate nonradiative processes following optical excitation. In a low-temperature calorimeter, the sample is irradiated with monochromatic light. The absorbed energy which is converted into phonons leads to a measurable increase of the sample temperature. The lowest detectable dissipated energy is 2·10−12J at a working temperature of 0.03 K. We demonstrate our method with a calorimetric absorption spectrum of J-aggregate monolayers of 1-methyl-1′-octadecyl-2,2′-cyanine. From this spectrum the emission quantum efficiency is obtained as a function of excitation wavelength. A relative minimum is found at the long wavelength edge of the absorption band at 582.5 nm.
TL;DR: In this article, a glass laser rod is covered by an envelope of highly fluorescent dyes emitting in the maximum absorption band of the ion, and radiation emitted from the dye is trapped in the glass rod by multiple reflections and absorbed by the ion.