Showing papers on "Extended X-ray absorption fine structure published in 1973"
TL;DR: In this paper, the optical absorption spectra of amorphous and crystalline thin Wo3 films have been measured in the temperature range 110° to 500°K and the temperature coefficient of the band edges was found to be − 5.0 × 10−4 eV/°K.
Abstract: Thin films of Wo3 deposited on quartz substrates at room temperature have been shown to be amorphous in structure. The optical absorption spectra of the amorphous and crystalline films have been measured in the temperature range 110° to 500°K. The fundamental absorption edge of an amorphous film occurs at 3800 A which on crystallization moves to 4500 A. On the high-energy side of the absorption edge several absorption peaks are resolvable in both types of film. The frequency dependence of the absorption coefficient below 104 cm−1 is described by an expression of the form K (v, T) = K 0 exp[− (β/kT) (E 0 − hv)] and above 104 cm−1 it follows a square law dependency. The temperature coefficient of the band edges was found to be − 5.0 × 10−4 eV/°K and the estimated band gaps at 0°K were found to be 3.65 and 3.27 eV for the amorphous and crystalline films, respectively. The electrical conductivity of a thin film has been measured in the temperature range 298–573°K and the activation energy was found t...
933 citations
TL;DR: In this article, the authors measured the absorption coefficient of a number of potential i.r.t. laser window materials and found that the absorption coefficients of LiF, CaF2, BaF2 and SrF2 all decrease exponentially with increasing wavelength.
121 citations
47 citations
TL;DR: In this paper, two-quantum transitions in Molecules and Molecular Crystals were studied and two-photon Absorption in Semiconductors and Ionic Crystals.
Abstract: CONTENTS 1. Introduction 299 2. General Relations for Two-Photon Transitions 299 3. Experimental Technique 301 4. Two-Quantum Transitions in Molecules and Molecular Crystals 302 5. Two-Photon Absorption in Semiconductors and Ionic Crystals 308 References 318
42 citations
TL;DR: In this paper, experimental measurements of the absorption cross sections of the sharp $4}A_{2}\ensuremath{\rightarrow}^{2}E$ transitions in triply charged chromium ions in MgO are described.
Abstract: Experimental measurements of the absorption cross sections of the sharp $^{4}A_{2}\ensuremath{\rightarrow}^{2}E$ transitions in triply charged chromium ions in MgO are described. The measured $R$-line absorption strength per ion is in good agreement with the value calculated by Macfarlane. Values for the absorption strengths of the $N$ lines are obtained and are shown to be consistent with what is known from fluorescence studies about the dipole nature of these transitions. Some sharp lines are seen in absorption which do not appear in fluorescence and the possibility that these are caused by transitions originating on chromium ions in rhombic sites is discussed.
36 citations
TL;DR: In this paper, an aluminum film formed by evaporation at 25 K onto a similar film previously deposited at room temperature displayed a featureless optical spectrum in the range 0.6-3.5 eV, the characteristic (200) peak being completely absent.
Abstract: An aluminum film formed by evaporation at 25 K onto a similar film previously deposited at room temperature displayed a featureless optical spectrum in the range 0.6-3.5 eV, the characteristic (200) peak being completely absent. A closer analysis showed the absorption to consist of a Drude term ($\ensuremath{\hbar}{\ensuremath{\omega}}_{p}=7.45$ eV; $\ensuremath{\tau}=3.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ sec) and what is believed to be interband absorption, possibly associated with a residual (111) absorption band.
33 citations
TL;DR: A method has been devised, based on the Kubelka-Munk theory of diffuse reflectance, for obtaining an estimate of the optical absorption coefficient of a finely powdered material that has been collected on the surface of a membrane filter.
Abstract: A method has been devised, based on the Kubelka-Munk theory of diffuse reflectance, for obtaining an estimate of the optical absorption coefficient of a finely powdered material that has been collected on the surface of a membrane filter. The procedure does not require any knowledge of either the real refractive index or particle size distribution of the material. No mechanical or chemical processing is involved, and only one sample is required. Results of experimental tests on materials of known absorption coefficient are presented.
31 citations
30 citations
26 citations
TL;DR: In this paper, a quantitative model is derived to interpret the nature and the role of sulfur ions in the photochromic chlorosodalite material, and the spectral properties of photo-induced color absorption, luminescence and cathodoluminescence are investigated.
Abstract: Synthetic.photochromic sulfo-chlorosodalite, 6(NaAlSiO4) ·2 NaCl(S), has been thoroughly investigated by measurements of optical absorption, photo-luminescence and cathodoluminescence. Depending on the sulfur ion form and concentration, the doped sodalite exhibits either sensitive tene-brescence or photoluminescence with long wavelength UV excitation. The photo-induced color absorption peaks at 5260A at 300°K with absorption coefficient, Δαmax >200 cm−1 . This is by far the highest photo-induced absorption observed for synthetic chlorosodalite. At 80°K, the peak position of the absorption does not show significant shift within instrumental accuracy. In photoluminescence, the emission spectra as well as the excitation spectra are studied at both 300 and 78°K. Four characteristic spectral bands (IR, blue, red, and a band with oscillation in wavelength) are observed. The oscillatory S2
- ion emission band starting about 2.35 eV and extending to lower energy and the IR band peaked at 1.4 eV are most efficiently excited by 3660A (3.4 eV), whereas the blue luminescence peaked at 2.7 eV has an excitation threshold of 3.9 eV. The red band is often masked by the oscillatory band and can be observed by higher energy excitation. The red and blue bands are also observable in the cathodoluminescence measurements of the sulfur-doped samples but not the undoped samples. Correlating the absorption, luminescence, and excitation spectral results, a quantitative model is derived to interpret the nature and the role of sulfur ions in the photochromic chlorosodalite material.
21 citations
TL;DR: In this article, the authors measured the chemical shifts of the x-ray K −absorption edge of cobalt in the compounds CoF2, CoO, Co2O3, Co(CH3COO)2· 4H2O, CoC2O4· 2H 2O,CoCl2· 6H 2 O, CoBr 2, CoS, CoCO3, and Co3(PO4)2 8H 2
Abstract: We have measured the chemical shifts of the x‐ray K ‐absorption edge of cobalt in the compounds CoF2, CoO, Co2O3, Co(CH3COO)2· 4H2O, CoSO4· 7H2O, CoC2O4· 2H2O, CoCl2· 6H2O, CoBr2, CoS, CoCO3, and Co3(PO4)2 8H2O. The chemical shifts have been found to vary linearly with the product i m2, where i is the ionicity and m the valence. We have also measured the fine structure observed on the high energy side of the edge in the metal and in the first six compounds. The positions of maxima and minima have been compared with theoretical predictions. The first absorption maximum in the metal has been interpreted as a plasma absorption. The bond lengths have been estimated from the fine structure.
TL;DR: Theoretical studies as mentioned in this paper show that it should be possible to determine whether the absorption at 10.6 μm in alkali halides is due to impurities or whether it is intrinsic.
Abstract: Theoretical studies are presented which show that it should be possible to determine whether the absorption at 10. 6 μm in alkali halides is due to impurities or whether it is intrinsic. These studies show that the temperature dependence of the measured absorption should be very different for intrinsic multiphonon absorption as compared with defect‐activated absorption.
01 May 1973
TL;DR: In this article, the T 1 absorption and emission spectra of the α-phase of Dichlorobenzene were analyzed and the frequency of the b 2g mode, involving out-of-plane chlorine motions, was found to drop by 210 cm −1 upon excitation and, as a result, it is active as a progression-forming mode in both the absorption and emissions spectra.
Abstract: The T 1 absorption and emission spectra of the recently discovered α-phase of p -dichlorobenzene are presented and analyzed. New high resolution spectra of the α-phase are also reported and the analysis of the T 1 absorption spectrum is revised in light of results for the γ-phase. The frequency of the b 2g mode, involving out-of-plane chlorine motions, is found to drop by 210 cm −1 upon excitation and, as a result, it is active as a progression-forming mode in both the absorption and emission spectra. Its activity, relative :othe a g modes, is quite different in the two phases of p -dichlorobenzene and is not the same in the absorption and emission spectra. The high resolution phosphorescence spectrum of the α-phase shows detailed fine structure due to both multiple site emission and to splittings of some of the ground state vibrational levels.
TL;DR: In this paper, the two-photon absorption of an optical (laser) and an x-ray quantum is considered within the context of the Born approximation and a simple expression relating the twophoton and onephoton photoionization absorption coefficients is obtained.
TL;DR: In this article, the choice of a window material suitable for high power CO2 laser emitting at 10.6 μm is discussed, with particular reference to the high resistivity form which is necessary to reduce free-carrier absorption to an acceptable level.
Abstract: The choice of a window material suitable for high power CO2 lasers emitting at 10.6 μm is discussed. Gallium arsenide was chosen and its preparation is discussed at length. The physical, electrical and optical properties of GaAs are also discussed with particular reference to the high-resistivity form which is necessary to reduce free-carrier absorption at 10.6 μm to an acceptable level. The method used to measure the optical absorption coefficient is a calorimetric one making use of a low power CO2 laser. The variation of the optical absorption coefficient with impurities, different dopants, resistivity, laser beam polarization and various growth parameters has been examined. It was found that GaAs could be routinely prepared with an absorption coefficient below 0.02 cm-1 at 10.6 μm, a minimum value of 0.005 cm-1 being the best observed. The prime cause of this absorption has not yet been established, but the need for further theoretical work is clear. The quality of the GaAs prepared makes it a prime candidate for a window material in high power CO2 lasers and systems.
TL;DR: For mixtures of Xe (0.2-20 kg/cm2) and Ar (5-40 kg/ cm2), the absorption coefficient has been measured in the range 0.1 cm-1 as discussed by the authors.
Abstract: Absorption coefficient κυ for mixtures of Xe (0.2–20 kg/cm2) and Ar (5–40 kg/cm2) has been measured in the range 0.1 cm-1
TL;DR: The results of a calorimetric measurement of the absorption coefficients of a single crystal of potassium dihydrogen phosphate at a wavelength lambda = 1.06 microm are reported and are shown to be in good agreement with values reported earlier.
Abstract: The measurement of the absorption coefficient of highly transparent materials using Pinnow and Rich’s calorimetric technique requires that the material be fabricated into the shape of a cylindrical rod. Since crystalline materials are more readily fabricated into rods with a square cross section, Pinnow and Rich’s calorimetric technique is extended to such samples. This is accomplished by calculating the temperature distribution that is produced in a sample of material having a square cross section by the passage of a Gaussian light beam through the sample. A simple relationship between the sample surface temperature and its absorption coefficient is derived that is valid to within 2% of the exact relationship for typical conditions that occur when employing the calorimetric method. The results of a calorimetric measurement of the absorption coefficients of a single crystal of potassium dihydrogen phosphate at a wavelength λ = 1.06 μm are reported. These are shown to be in good agreement with values reported earlier that were obtained by U. S. Averbakh, I. A. Batyrea, and V. O. Bespalov using a spectrophotometric technique.
TL;DR: In this article, a 50 cm bent-quartz crystal vacuum spectrograph was used to obtain the chlorine K absorption spectra of PdCl2, CdCl 2, and FeCl3 for the first transition metal dichlorides.
Abstract: The chlorine K absorption spectra of PdCl2, CdCl2, and FeCl3 have been obtained with a 50‐cm bent‐quartz‐crystal vacuum spectrograph. A prominent absorption maximum has been detected at the threshold and is interpreted in terms of the electron transfer model. Results are evaluated by comparing the obtained spectra with the chlorine K absorption spectra of the first‐transition metal dichlorides reported previously. Chemical shifts are found for the first absorption band and discussed in relation to the ionization potentials of the metal ions and the lattice energy. The chlorine K absorption spectra of the chlorides are discussed in relation to the crystal structure.
TL;DR: In this article, the optical energy gap of vitreous GeSb2Se4 was determined in spectral region 0.7-25 μm and measured reflectivity curves were used to estimate the value of the refractive index.
Abstract: Optical absorption of vitreous GeSb2Se4 was studied in spectral region 0.7–25 μm. At low absorption levels near the edge the absorption coefficient K depends exponentially on energy. At high absorption levels the quadratical energy dependence of K is observed. In the present work we determined the optical energy gap Eoptg = 1.29 eV and discussed the temperature dependence of the absorption coefficient. Measured reflectivity curves were used to estimate the value of the refractive index of GeSb2Se4 ( n = 3.13–3.56 at h ω = 1.00–1.70 eV ). Vitreous GeSb2Se4 is also transparent in the spectral interval 2–15.7 μm.
TL;DR: In this paper, the authors measured the transmittances as a function of pressure in the troughs between self-broadened vibration-rotation lines in the 5·3 μ fundamental band of NO indicate more absorption than expected for Lorentzian-shaped lines at a displacement greater than 1 cm-1 from the line center.
Abstract: Measurements of the transmittances as a function of pressure in the ‘troughs’ between self-broadened vibration-rotation lines in the 5·3 μ fundamental band of NO indicate more absorption than expected for Lorentzian-shaped lines At a displacement greater than 1 cm-1 from the line center, ν0, a better representation is provided by an absorption coefficient proportional to |ν−ν0|-16
TL;DR: In this article, the authors measured the optical absorption edges at 300 K and 80 K for single crystals of the compounds ZnSiP2, Zn SiP1.5As 0.5, ZnsSiP1As 1.5 and ZnsiP2.
Abstract: Optical absorption edges at 300 K and 80 K have been measured for single crystals of the compounds ZnSiP2, ZnSiP1.5As0.5, ZnSiP1As1, ZnSiP0.5As1.5 and ZnSiAs2. Exponential absorption edge tails were observed in all cases. The minimum energy gap increases from ZnSiAs2 through the range to ZnSiP2; a value of approximately 2.0 eV at 300 K for ZnSiAs2 agrees with previous results, but the value of approximately 2.5 eV for ZnSiP2 is significantly higher than previous measurements.
TL;DR: The fine structure of the L111 absorption edge of rhenium in its freshly prepared five complexes has been investigated with a 1 m curved mica crystal spectrograph as mentioned in this paper.
Abstract: Fine structure of the L111 absorption edge of rhenium in its freshly prepared five complexes has been investigated with a 1 m curved mica crystal spectrograph. A prominent absorption maximum (white line) has been detected at the L111 edge. Chemical effects on the fine structure are restricted in the energy region lying within nearly 100 eV of the main edge. It appears that the EFS is independent of the symmetry of the absorbing crystal. The shape of L111 edge suggests octahedral coordination for rhenium in the complexes under investigation. Bond lengths are determined employing x‐ray fine structure methods. It is found that the present results favor Lytle's method for the metal and that of Levy's for complexes.
TL;DR: In this article, absolute absorption coefficients in the region of the M4 and M5 edges are presented for cerium in CeF3, CeO2 and in the metal strong line absorptions (3d to 4f) occur to the low energy side of weak M 4 and M 5 'edges' at each edge the absorption passes through a weak broad peak attributed to transitions into a band of higher f states.
Abstract: Absolute absorption coefficients in the region of the M4 and M5 edges are presented for cerium in CeF3, CeO2 and in the metal Strong line absorptions (3d to 4f) occur to the low energy side of weak M4 and M5 'edges' At each 'edge' the absorption passes through a weak broad peak attributed to transitions into a band of higher f states The spectra of CeF3 and the metal at room temperature are structurally similar but differ clearly from the quadrivalent oxide A shift to higher energy is found for both absorption lines and edges in the sequence fluoride-oxide-metal at room temperature On cooling the evaporated metal absorption foil ( gamma phase) to 77 K both M4 and M5 line profiles change into forms accurately resolvable into a combination of trivalent (CeF3 like) and quadrivalent (CeO2 like) curves, suitably displaced in energy, in the proportion 59% to 43% respectively
TL;DR: In this paper, the absorption spectrum of Cr3+ ions in the ground (4A2) and metastable (2E) states, and of the luminescence spectrum of the same ions in Y3Al5O12 crystals at 300 and 77°K, were investigated.
Abstract: An investigation was made of the absorption spectrum of Cr3+ ions in the ground (4A2) and metastable (2E) states, and of the luminescence spectrum of the same ions in Y3Al5O12 crystals at 300 and 77°K. The effective absorption cross sections were determined for the 4A2 state. The luminescence deexcitation time was found to be 1.5 and 9 msec at 300 and 77°K, respectively. The absorption spectrum of the 2E state had four wide absorption bands with maxima at 16,700, 23,300, 28,600, and 40,500 cm–1. The theoretical energy level scheme of Cr3+ was calculated for Dq = 1725 cm–1, G = 640 cm–1, C = 3200 cm–1, v = 495 cm–1, and v' = 259 cm–1, making an allowance for the mixing of the ΓtrigS states. The experimentally observed absorption bands were attributed to specific transitions and the theoretical and experimental intensities were compared.
TL;DR: The absorption-rich optical and near-infrared spectrum of the quasi-stellar object 1331 + 170 is analyzed in this article, and at least three absorption systems are shown to be present; the absorption redshifts are 1.7755, 1.7851, and 1.9637.
Abstract: The absorption-rich optical and near-infrared spectrum of the quasi-stellar object 1331 + 170 is analyzed. The emission-line redshift is about 2.08, and at least three absorption systems are shown to be present; the absorption redshifts are 1.7755, 1.7851, and 1.9637. We conclude that the absorbing material giving rise to the three systems is intrinsic to the QSO despite the high velocity difference between emission and absorption systems and the low velocity dispersion within each absorption system.
TL;DR: In this paper, the two-photon absorption coefficient of proustite was measured at the ruby and neodymium laser wavelengths at pumping intensities up to 35 MW/cm2.
Abstract: The two-photon absorption coefficient of proustite was measured at the ruby and neodymium laser wavelengths at pumping intensities up to 35 MW/cm2: Its values were 0.1 and 0.03 cm/MW, respectively. The two-photon absorption exhibited no anisotropy associated with the polarization of the incident radiation. An analysis was made of the limiting influence of the two-photon absorption on the efficiency of parametric conversion.
TL;DR: In this paper, a computer calculation model is described and used to calculate intense light absorption over the wavelength range 0.1?m??? 10.6?m for two different pulse durations.
Abstract: The efficiency of absorption of laser light by a deuterium plasma is an important parameter for the laser/pellet fusion application. A computer calculation model is described and used to calculate intense light absorption over the wavelength range 0.1 ?m ? ? ? 10.6 ?m for two different pulse durations. The calculation includes both collisional absorption and anomalous absorption by means of the parametric ion-acoustic instability. The general result for all of the computer calculations, supported by an analytic model, is that the absorption efficiency increases as the wavelength is decreased.
TL;DR: In this paper, a lower bound for the absorption coefficient of infrared transmitting materials was derived by calculating the absorption due to anharmonicity-induced multi-phonon processes.