Vibrational spectroscopy of indium-doped Pb0.9Mn0.1Te alloy

Raman scattering and far-infrared reflection spectra of 0.5 at.% In doped Pb_0.9Mn_0.1Te single crystal at temperatures between 10 and 300K are presented. The infrared spectra have been fitted using a modified plasmon-phonon interaction model with an additional oscillator (at about 122 cm^?1) representing a local In-impurity mode. Phonons in this mixed crystal exhibit intermediate mode behavior. The plasma frequency decreases on cooling from 300 to 25K and increases sharply between 20 and 10 K. The results of galvanomagnetic measurements are also presented.     

Optical phonons of circular wires in porous GaP

The reflection spectra of porous gallium phosphide samples are investigated in the far infrared region of wave numbers (10–700 cm^?1). In addition of the longitudinal and transverse optical phonon modes corresponding to the bulk material, additional vibrational modes are detected. Their number and spectral position are correctly described by a model of a dispersive dielectric medium under the assumption that porous gallium phosphide is formed by crystallites whose shape is close to cylindrical. It is concluded that such vibrational modes are optical phonons confined by the volume of the quantum wire. The experimental optical reflection spectra are used to obtain estimates of the average diameter of nanocrystallites forming the porous GaP layer.     

Far-infrared spectroscopy by synchrotron radiation at the UVSOR Facility

At the UVSOR Facility, Institute for Molecular Science, the practical use of the synchrotron radiation as a far-infrared light source has started. A spectroscopic system has been constructed at the beam line BL6A1 of UVSOR storage ring, which covers the wavenumber region from 5 to 250 cm^–1. The cross sectional diameter of the light beam at the sample position is as small as 3 mm with the angular divergence of about 100 mrad. The system has been made mainly for the transmission and reflection measurements of small samples with small angular divergence by the use of the high brightness of the synchrotron radiation. Examples of observed transmission and reflectivity spectra are shown.     

Infrared absorption and far-infrared diffuse reflection spectra in Pb-doped Bi?Sr?Ca?Cu?O high-temperature superconductor

In this paper we study the room-temperature infrared transmission spectra (400–1600cm^–1) and far-infrared diffuse reflection spectra (50–450cm^–1) in Pb-doped Bi–Sr–Ca–Cu–O (2223) single phase (Tc=107k, sp1), multiphase (Tc=110k, sp2) and nonsuperconducting samples (sp3). The spectral features in superconductor are totally different from those in nonsuperconductor, which show the different crystal structure. The correlation existing between a factor group analysis of the phonons in (2223) and (2212) compounds affords a tentative assignment of ir-active modes in Pb-doped (2223) single phase by comparison with reported data in (2212) materials. The Cu–O stretching E_u vibration (605cm^–1) of CuO₂ layers is the characteristic vibrational mode related perovskitelike crystal structures. Two phonon coupling effect emerges in the infrared transmission spectra in Pb-doped superconductor. The Ca–O vibration A_2u (254cm^–1) might be related to superconductivity of Bi-based family.     

Far-infrared spectra of Pb1−xMnxTe alloys

Far-infrared reflectivity spectra of Pb_1−xMn_xTe (0.0001x0.1) single crystals were measured in the 10–250 cm⁻¹ range at room temperature. The analysis of the far-infrared spectra was made by a fitting procedure based on the model of coupled oscillators. In spite of the strong plasmon–LO phonon interaction, we found that the long wavelength optical phonon modes of these mixed crystals showed an intermediate one–two mode behavior.     

The far infrared complex reflectivity of GaTe

The room temperature polarized complex (amplitude and phase) infra-red reflection spectra of single crystal monoclinic GaTe have been measured between 20 and 400 cm^–1 using a dispersive Fourier transform spectrometer. The measurements allow the experimental zone centre transverse and longitudinal phonon modes and optical constants to be determined without recourse to oscillator fit models or Kramers-Kronig analysis. Infrared power transmission measurements have allowed all fifteen predicted modes to be identified and the results are compared to recent Raman work.     

Far-infrared reflectivity of KI:Cl? and KI:Na+

The far-infrared reflectivity spectra of KI doped with 1% Cl^– and 2% Na⁺ were measured using a dual cavity technique. In addition to the observation of all previously-observed resonant and gap modes, several features were discovered in and near the optic band. A new gap mode at 90 cm^–1 in KI:Cl^– was discovered. In both systems sharp, narrow reductions in reflectivity at 98, 108, 116, and 139 cm^–1 were observed, as was a general reduction in reflectivity between 108 and 139 cm^–1. The structure at 98 and 116 cm^–1 is most-likely due to optical activity induced in normally inactive lattice modes by the high concentration of impurities. The features at 108 and 139 cm^–1 and the reduction in reflectivity between them were shown by a simple model calculation to be due to an increase in damping of the TO phonon.     

Nuclear magnetic resonance study of langatate

A langatate crystal was studied using the nuclear magnetic resonance method. The temperature dependence of the spin-lattice relaxation rate of ⁷¹Ga nuclei was measured in a single-crystal sample in the range 294–500 K. It was shown that the relaxation rate depends linearly on the square of the temperature. The shape of the powder spectrum obtained under static conditions was found to correspond to large values of the quadrupole coupling constant of gallium nuclei. The measurements of the powder spectra obtained upon magic-angle spinning made it possible to estimate the quadrupole coupling constant for gallium in the tetrahedral and octahedral oxygen coordinations.     

Determination of the gap distribution in YBa2Cu3O7 using a far-infrared reflection-Fabry-Pérot device

This paper reports on far-infrared measurements of YBa₂Cu₃O₇ films oriented with the c-axis perpendicular to the surface, by using a silicon reflection Fabry-Pérot interferometer as a multireflection device. From these we could derive the dielectric function, the refractive index, the field penetration depth and the surface impedance of the material. The one order of magnitude higher sensitivity of the method compared to a direct reflectance measurement allowed to find an almost continuous gap distribution in the 70–215 cm^–1 region together with a separate gap at about 330 cm^–1. A quasizero gap absorption is found down to 20 cm^–1 even at low temperatures (10 K).     

Magneto-optical measurements with a hybrid magnet

An FFT spectrometer has been constructed to measure magneto-optical spectra in the far-infrared region (3 to 40 cm^–1) with a hybrid magnet system. The magneto-absorption was studied in the spin-Peierls cuprate CuGeO₃ at various magnetic fields. Coil constants of superconducting magnet and resistive one, of which a hybrid magnet consists, were calibrated by ESR spectra at the constant field.     

Behavior of copper in gallium arsenide with a high tellurium concentration

The electrophysical properties and cathode luminescence spectra of gallium arsenide with a high tellurium concentration (n = 2·10¹⁸ cm^–3) alloyed with copper are investigated under different diffusion conditions. Centers are determined from measurements of the Hall effect with an ionization energy of 0.190 ± 0.006 eV whose concentration does not depend on the arsenic vapor pressure (0.1 and 1 atm) and the cooling rate of the samples from the diffusion temperature. A band with h_m = 1.30–1.32 eV whose intensity depends on the cooling conditions of the samples was observed in the cathode luminescence spectra of these samples. The nature of the observed defects is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 93–99, July, 1979.In conclusion of this article the authors express their gratitude to L. K. Tarasova for preparation of the samples.     

Carrier scattering mechanisms in manganese-doped gallium antimonide

The results are given of an investigation of the galvanomagnetic properties of manganese-doped gallium antimonide in the interval of temperatures 4.2–300°K and in magnetic fields up to 1.5 T. The manganese was introduced into the melt during zone melting in concentrations in the range 0.005–1 at.%. The samples possessed p-type conduction. It was shown that manganese forms in gallium antimonide a shallow acceptor level with ionization energy 16 ± 3 meV. The cluster mechanism makes a significant contribution to the carrier scattering in the considered temperature range. The parameters of this scattering mechanism were determined. It was shown that with increasing concentration of manganese in the sample the contribution to the mobility of the mechanism of carrier scattering by space-charge regions increases.Translated from Izvestiya Vysshikh Uchebnykh Zavedennii, Fizika, No. 1, pp. 53–57, January, 1992.We thank I. I. Burdinyan and D. D. Nedeoglo for constant interest in the work.     

Water Vapor Measurements between 590 and 2582 cm: Line Positions and Strengths

This study involves measurements of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O vapor spectra for the region between 590 and 2582 cm⁻¹. The parameters derived from the data include line positions, energy levels, and linestrengths. The study involves high-resolution line-position measurements with samples at room temperature in the (000)–(000), (010)–(010), and (010)–(000) bands. The experimental frequencies were used along with microwave, far-infrared, and hot water emission measurements in an analysis to obtain high-accuracy rotational energy level values in the (000), and (010) vibrational states of H₂¹⁶O forJ≤ 20. The experimental linestrengths were fitted by least squares to a model in which the dipole moment was represented as a series expansion containing up to 19 dipole moment matrix elements. The measurements in this work were more extensive than reported in prior studies by this author for the (010)–(000) band.     

Far-infrared reflection spectra of Pdo,PdS, PdSe and PtS

The far-infrared reflection spectra of PdO, PdS, PdSe and PtS have been recorded in the frequency range from 700 to 30cm⁻¹. From Kramers-Kronig analysis the TO-and LO-phonon frequencies (|q| = 0) were determined for PdO, PdS and PtS. Strongly temperature-dependent free-carrier contributions to the reflection spectrum of PdSe were observed. A nearly zero band gap of PdSe is discussed with regard to being responsible for this behaviour.     

Far IR spectra of Ag<Subscript>2</Subscript>CdI<Subscript>4</Subscript> at temperature range 10–420 K: complementary experimental and first-principle theoretical study

The influence of temperature on the far-infrared (FIR) spectrum of polycrystalline Ag₂CdI₄ has been investigated by Fourier Transform Infrared (FTIR) spectroscopy measurements. The FIR phonon spectrum has also been calculated by means of quantum mechanical density functional theory (DFT). The comparison of calculated and measured spectra allows the fast and reliable assignment of the measured phonon modes, and thus clarifies the mode splitting character obtained at elevated temperatures.     

Halogen-substituted amides. VI—vibrational spectra of some fluoro- and iodo-substituted acetamides

The Raman spectra of 2-fluoroacetamide, trifluoroacetamide and 2-iodoacetamide were recorded and their infrared spectra as mulls were measured in the range 4000–200 cm⁻¹. The Fourier transform far-infrared spectra of the same samples, in the region 500–50 cm⁻¹, were also obtained. The frequencies were assigned to various fundamental modes of the molecules on the basis of qualitative considerations.     

FAR-INFRARED AND INFRARED REFLECTIONS OF Tl2Ba2Ca2Cu3O10 FILM

The far-infrared and infrared reflection spectra of Tl₂Ba₂Ca₂Cu₃O₁₀ superconducting film are reported in this paper. It is found there are three sharp reflection edges in both the superconducting and normal states, their positions being near ≈ 150, ≈ 350 and ≈600 cm^-1. We attribute these reflection spectra to the Drude free carriers and a wide mid-infrared absorption band. When the incident angle increases from 7° to 30°, some additional stractures appear in the refiection spectra, which are the A_2u phonon modes vibrating along c-axis.     

Far-infrared spectroscopy of CdTe1−xSex(In): Phonon properties

The far-infrared reflectivity spectra of CdTe_0.97Se_0.03 and CdTe_0.97Se_0.03(In) single crystals were measured at different temperatures. The analysis of the far-infrared spectra was carried out by a fitting procedure based on the dielectric function which includes spatial distribution of free carriers as well as their influence on the plasmon–phonon interaction. We found that the long wavelength optical phonon modes of CdTe_1−xSe_x mixed crystals exhibit a two-mode behavior. The local In mode at about 160 cm⁻¹ is observed. In both sample, a surface layer with a low concentration of free carriers (depleted region) are formed.     

BH4− Induced far-infrared absorption in the phonon gap of KI

High resolution measurements of the far-infrared lattice gap modes due to BH₄^? in KI are reported. The observed bands at 85.45 ± 0.05 and 84.94 ± 0.05 cm^?1 are ascribed as resulting from the presence of two stable boron isotopes in the BH₄^? ion. The gap modes are calculated by allowing for the elastic relaxation of the lattice around the impurity. The results of a calculation for the Br^? gap modes in KI are also presented.     

Far-infrared spectra of imperfect YBaCuO films on Si substrates

We have measured the far-infrared (FIR) transmittance of low conductivity, imperfect YBCO films deposited on Si, at both 300 K and 20 K. Test reflectance measurements were also performed at room temperature. Our aim was both to study YBCO phonons by transmission measurements and to check if FIR spectra of imperfect YBCO films can be described in the framework of the BCS theory. In order to describe our measurements, we provide exact expressions for both transmittance and reflectance, averaged with respect to the interference fringes of the substrate. By modelling the complex dielectric constant of the film, we then study the YBCO phonons which are evident in the measured spectra. The comparison between spectra of normal and superconducting phases shows that the superconducting transition affects our spectra only at very low frequencies. By considering a two fluid model in which only a small fraction of electrons becomes superconducting and by assuming an energy gap of the order of 130 cm⁻¹, we find that our data can be explained in terms of the Mattis-Bardeen theory.