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Showing papers on "Absorption spectroscopy published in 1974"


Journal ArticleDOI
TL;DR: In this article, a simple rectangular potential well with a depth of ≈088ΔE g, where ΔE g is the difference in the semiconductor energy gaps is defined.
Abstract: Quantum levels associated with the confinement of carriers in very thin, molecular-beam—grown AlxGa1−xAs−GaAs-Alx Ga1−xAs heterostructures result in pronounced structure in the GaAs optical absorption spectrum Up to eight resolved exciton transitions, associated with different bound-electron and bound-hole states, have been observed The heterostructure behaves as a simple rectangular potential well with a depth of ≈088ΔE g , for confining electrons and ≈012ΔE g for confining holes, where ΔE g is the difference in the semiconductor energy gaps

976 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrated that frequency-sweep excitation can provide the broad-band irradiation required to excite ion cyclotron resonances throughout any desired mass range.

355 citations


Journal ArticleDOI
TL;DR: In this paper, the authors discussed the fluorescence and optical properties of reduced flavins and flavoproteins and found that the 4a,5-dihydroflavin chromophore exhibits a strong fluorescence that is maximal around 520 nm.
Abstract: Publisher Summary This chapter discusses the fluorescence and optical characteristics of reduced flavins and flavoproteins. Flavins and flavoproteins in their oxidized state (Flex) are typically yellow, with the absorption spectrum in the visible and near-ultraviolet (UV) range being characterized, by two well-resolved bands centered around 450 and 370 nm. This chromophore, free in solution, exhibits a strong fluorescence that is maximal around 520 nm; when the chromophore is bound to flavoproteins, its emission can be fully quenched. Studies show that the near-UV absorption spectrum of the 4a,5-dihydroflavin chromophore is similar, in its appearance, to that of its 1,5-dihydro isomer, but its shape is even more dependent on temperature and solvent. In particular, substituents that have an effect on the internal mobility of the molecule were found to cause major spectral changes on the chromophore free in solution and also when bound to various apoflavoproteins. At ambient temperature, 4a,5-dihydroflavins show a weak fluorescence only when an appropriate substituent decreases their internal mobility. However, at low temperature in rigid ethanol glasses or when bound to apoflavoproteins, 4a,5-dihydroflavins exhibit a rather strong fluorescence emission maximal in the range 480-530 nm.

349 citations


Journal ArticleDOI
TL;DR: In this article, a narrow (Δ≈0.7 cm −1 ), long-lived (τ≈some hours) gap in broad-band absorption spectra of perylene and 9-aminoacridine in ethanol at 4.2 K has been discovered and investigated.

338 citations



Journal ArticleDOI
TL;DR: In this paper, the complete absorption difference spectrum of the primary electron acceptor of Photosystem II has been measured at room temperature in subchloroplast fragments prepared with deoxycholate and the shape and amplitude of the spectrum indicate that the primary reaction involves the reduction of one bound plastoquinone molecule per reaction center to its semiquinone anion.

262 citations


Journal ArticleDOI
TL;DR: In this paper, a cw difference-frequency spectrometer was developed for the 2.2 to 4.2 μm infrared region by mixing argon and tunable dye lasers in LiNbO3.
Abstract: A cw difference-frequency spectrometer has been developed for the 2.2 to 4.2 μm infrared region by mixing argon and tunable dye lasers in LiNbO3. A resolution of 5 × 10−4 cm−1 with continuous scans up to 1 cm−1 and a scan precision better than 2 × 10−3 cm−1 have been achieved. Tunable ir powers of ~1 μW have been obtained, enabling sensitive absorption measurements and real-time spectroscopy. The range, resolution, speed, and sensitivity of this difference-frequency technique are demonstrated by absorption traces of water vapor, ammonia, methane, and nitrous oxide.

230 citations



Journal ArticleDOI
TL;DR: In this paper, the resonance Raman spectra of β-carotene in isopentane solution have been obtained at low temperature, using eight output lines of the argon-ion laser and a line of the heliumcadmium laser.

183 citations


Book
01 Jan 1974

171 citations


Journal ArticleDOI
TL;DR: The strongest and generally most useful optical absorption lines include the D lines of Na I, the H and K lines of Ca II, and the resonance doublet at 7600 A and 7664 A of K I.
Abstract: The strongest and generally most useful optical interstellar absorption lines include the D lines of Na I, the H and K lines of Ca II, and the resonance doublet at 7600 A and 7664 A of K I. The interferometric data for these strongest atomic lines are examined in a comprehensive manner. The numerical results pertaining to the total column densities are collected in a table, which lists 82 stars. The correlations among some of the quantities listed in the table are displayed in a number of graphs.


Journal ArticleDOI
TL;DR: In this paper, the ground state vibrational spacings of the van der Waals molecule Xe2 have been extracted from the vibronic structure of two electronic transitions, and an extrapolation procedure based on an assumed inverse sixth power long-range potential reveals that the ground electronic state supports 25 or 26 bound vibrational levels.
Abstract: The vacuum ultraviolet absorption spectrum of the van der Waals molecule Xe2 has been photographed at high resolution. Ground state vibrational spacings ΔG(v+½) with v = 0–9 have been extracted from the vibronic structure of two electronic transitions. An extrapolation procedure based on an assumed inverse sixth power long‐range potential reveals that the ground electronic state of Xe2 supports 25 or 26 bound vibrational levels. Spectroscopic values for the well depth, 195.5 cm−1, and zero‐point energy, 10.4 cm−1, are compared to results from recent molecular beam scattering experiments. The shapes of the spectroscopic and scattering potentials are examined by means of Rydberg‐Klein‐Rees plots of well depth vs well width.

Journal ArticleDOI
TL;DR: A method developed by previous workers for measuring the absorption coefficient of strongly absorbing powdered materials has been applied to samples of atmospheric dust in the 0.3-1.1-microm wavelength interval, and the corresponding imaginary refractive index is calculated.
Abstract: A method developed by previous workers for measuring the absorption coefficient of strongly absorbing powdered materials has been applied to samples of atmospheric dust in the 0.3-1.1-microm wavelength interval. This work, which is based on the Kubelka-Munk theory of diffuse reflectance, provides an estimate of the optical absorption coefficient. The corresponding imaginary refractive index is calculated from this value. Results are given for several samples of dry atmospheric dust collected in the desert of southern New Mexico. A typical value for the imaginary refractive index was found to be 0.007 at 0.6 microm, with little dependence on wavelength in the spectral range investigated. These results are found to be in good agreement with those of other workers obtained by different methods.


Journal ArticleDOI
C. C. Grimes1, T. R. Brown1
TL;DR: In this article, the first direct spectroscopic study of electrons bound in imagepotential-induced surface states outside liquid helium was presented, where absorption lines showed the expected linear Stark effect in the presence of an electric field.
Abstract: We present the first direct spectroscopic study of electrons bound in image-potential-induced surface states outside liquid helium. We have observed absorption lines which show the expected linear Stark effect in the presence of an electric field. Zero-field splittings extrapolated from the data are 125.9 and 148.6 GHz for electronic transitions from the ground state to the first two excited states in the image-potential well.


Journal ArticleDOI
TL;DR: In this article, the electronic absorption spectra of symmetrical and asymmetrical trihalide ions (I3−, IBr2− and ICl2−, Br3− and BrCl 2−) are presented.

Journal ArticleDOI
TL;DR: In this article, the identification of HO2 as the absorbing molecule is based on a partial analysis of the spectra and on a variety of different chemical methods used to produce the radical.
Abstract: Far‐infrared absorption spectra of HO2 in the gas phase have been detected at six wavelengths of a water vapor laser magnetic resonance spectrometer. The identification of HO2 as the absorbing molecule is based on a partial analysis of the spectra and on a variety of different chemical methods used to produce the radical. Approximate values of rotational constants and spin doublet separations are derived from the spectra.

Journal ArticleDOI
TL;DR: In this article, an extra absorption band with two peaks is observed at the low energy region of the absorption edge for Fe-doped CuAlS 2 and CuGaS 2, respectively.
Abstract: Optical absorptions have been measured in chalcopyrite, CuFeS 2 , and Fe-doped CuAlS 2 and CuGaS 2 An extra absorption band with two peaks is observed at the low energy region of the absorption edge for Fe-doped CuAlS 2 and CuGaS 2 Energy positions of two absorption peaks are 13 eV and 20 eV for CuAlS 2 and 12 eV and 19 eV for CuGaS 2 , respectively The intensity of this absorption band increases with the increase of doped Fe ions and grows into the absorption edge of CuFeS 2 Its oscillator strength comes up to 7·10 -2 In chalcopyrite photoconductivity is observed and its maximum is just at the same energy region of the absorption edge By comparing our results with those of absorption measurements for Cu- or Fe-doped ZnS it is concluded that this absorption band originates from the charge transfer transitions relating to 3d electron of Fe ions and the absorption edge of CuFeS 2 rises from the band-to-band transition corresponding to this charge transfer transition

Journal ArticleDOI
TL;DR: In this paper, a nanosecond laser spectrometer consisting of a 3nsec ruby/Nd PTM laser, fast detection system and high brightness analysing source is described.

Journal ArticleDOI
TL;DR: A laser absorption spectrometer, using an ir laser transmitter and a heterodyne radiometer, can be used from an aircraft or spacecraft to measure altitude profiles of air pollutants and other atmospheric constituents.
Abstract: A laser absorption spectrometer, using an IR laser transmitter and a heterodyne radiometer, can be used from an aircraft or spacecraft to measure altitude profiles of air pollutants and other atmospheric constituents. The technique involves measurement of differential absorption at several wavelengths, using the diffusely reflecting earth's surface to provide a return signal. The pressure broadening of absorption lines allows one to discriminate between high and low altitude absorbers. Application of the technique to measurements of ozone, nitric oxide, and water vapor are presented. CO2 and CO lasers are considered as transmitters. The discussion includes altitude resolution limitations, atmospheric temperature dependence, and frequency stability requirements of the instrument.

Journal ArticleDOI
TL;DR: In this article, the ESR and visible absorption spectra of a number of bis(salicylidenealkylaminato)copper(II) complexes with different kinds of alkyl groups were measured in toluene.
Abstract: The ESR and visible absorption spectra of a number of bis(N-salicylidenealkylaminato)copper(II) complexes with different kinds of alkyl groups were measured in toluene. The coordinations of these complexes in toluene are distorted towards a tetrahedral geometry to varying extents; the relationship between the degree of the distortion and the ESR and visible absorption parameters was systematically investigated. Especially, the experimental fact that the absolute values of the hyperfine coupling constant with the copper nucleus decrease with an increase in the degree of distortion was discussed. A configurational equilibrium between two species with different degrees of the distortion was found to exist for the complexes with R=isopropyl and cyclohexyl in toluene.


Journal ArticleDOI
TL;DR: In this article, the absorption of microwaves in a normally magnetized YIG disk has been measured and analyzed, and the absorption peaks are interpreted to be caused by magnetostatic waves propagating radially across the disk.
Abstract: The absorption of microwaves in a normally magnetized YIG disk has been measured and analyzed. The absorption peaks are interpreted to be caused by magnetostatic waves propagating radially across the disk. The mode numbers of absorption peaks are determined by the aspect ratio of the disk, (ω/γ)2−Hi2 and BiHi −(ω/γ)2, where ω is the microwave angular frequency, γ is the gyromagnetic ratio, and Hi and Bi are internal magnetic fields and depend upon the applied magnetic field. The experimental values of the applied magnetic field at which the absorption peaks are caused are in good agreement with the theoretical values. It has been verified both theoretically and experimentally that the new mode absorptions due to the magnetostatic waves exist in the case of ω/γ−[Bi(0)Hi(0)]1/2 =dH > 0, where Bi(0) and Hi(0) are the internal fields at the disk center. These new mode abosrption peaks tend to shift toward the cutoff point of the usual absorption spectra as the incident microwave power is increased.

Journal ArticleDOI
TL;DR: In this paper, an SCF Xα SW calculation using overlapping spheres has been carried out for ferrocene and the agreement with the observed optical absorption spectrum has been shown for d 1g (π-Cp) e 1u (π)-Cp e 2g (3d) a 1g(3d ) * 1g

Journal ArticleDOI
01 Dec 1974
TL;DR: In this paper, the adsorption and reaction of acetic acid have been studied using the technique of reflection-absorption infrared spectroscopy, and the results indicate that at ambient temperatures acetic acids adsorbs on cuprous oxide to form a vacuum stable (10−7 Torr), thick (several hundred angstrom) film having an ionic lattice comprised primarily of discrete protons and acetate ions.
Abstract: The adsorption and reaction of acetic acid have been studied using the technique of reflection-absorption infrared spectroscopy. Evaporated copper films on both glass and gold substrates have been oxidized to cuprous oxide and allowed to interact with gaseous acetic acid. The results indicate that at ambient temperatures acetic acid adsorbs on cuprous oxide to form a vacuum stable (10−7 Torr), thick (several hundred angstrom) film having an ionic lattice comprised primarily of discrete protons and acetate ions. At higher temperatures (near 200°C) incorporation of copper ions into the film occurs with apparent partial decomposition of the acetate ion. The general implications of these results on the understanding of the mechanisms of attack of organic acids on metal-metal oxide surfaces is discussed.

Journal ArticleDOI
TL;DR: Using a low-temperature evaporation technique, amorphous-state films of naphthacence, perylene, coronene and 1,12-benzoperylene were prepared, and their absorption and fluorescence spectra were measured as discussed by the authors.

Journal ArticleDOI
TL;DR: In this article, the absorption spectra of the first excited singlet S 1 and the first triplet T 1 of (OEP)SnCl 2 were determined from photolysis and spectroscopy.