Calculation and study of the ir absorption spectrum of 2,4-thiazolidinedione

The IR absorption spectrum is found for 2,4-thiazolidinedione in the range 400–3500 cm^–1, and the normal modes are calculated on the basis of a model for this molecule. The spectrum is interpreted.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 64–68, December, 1969.     

Calculation and study of the IR absorption spectrum of hydantoin

The IR absorption spectrum of hydantoin has been obtained in the range 400–3500 cm^–1, and the normal-vibration frequencies are calculated on the basis of the mechanical model. The spectrum is interpreted.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 6, pp. 116–120, June, 1969.     

IR absorption spectrum of hydrogen xanthane

The normal vibration frequencies of hydrogen xanthane are calculated on the basis of a mechanical model. The IR absorption spectrum was measured in the range 400–3600 cm^–1 for tablets of this substance with KBr and in vaseline and fluorinated oil. The spectrum is interpreted. The effects of the change in the structure of the cyclopentane molecule on the vibration spectrum and symmetry of the heterosubstituted molecules are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 50–54, November, 1970.     

The IR absorption spectrum of 2 - aminothiazolid - 4 - one

A mechanical model has been used to calculate the frequencies in the vibrational spectrum of the imine and amine tautomeric structures for this compound; the IR spectrum for the crystalline state has been deduced for the range 80–3500 cm^–1, and a discussion is given for the effect of the tautomeric prototropic forms on the vibrational spectrum.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 9, pp. 76–82, September, 1971.     

Calculation and investigation of infrared absorption spectrum of rhodanine

The IR absorption spectrum of rhodanine was obtained in the 400–3500 cm^–1 region. A full set of frequencies for the vibrational spectrum was determined by a mechanical model with C_s symmetry, and an interpretation of the bands in the IR spectrum of rhodanine is given. The change in the IR spectrum of cyclopentane when the structure of the ring is complicated by introduction of two heteroatoms is examined. It is shown that a sulfur atom reduces and a nitrogen atom increases the frequencies of the ring stretching vibrations. Successive increase in the number of heteroatoms in the cyclopentane ring lowers the D_5h symmetry of the molecule, but traces of high symmetry remain in the spectrum of rhodanine.     

Infrared vibrational spectra of -histidinium dihydrogen orthophosphate orthophosphoric acid (LHP)

The entire vibrational spectrum of a single crystal of -histidinium dihydrogen orthophosphate orthophosphoric acid (LHP) was studied by infrared (IR) spectroscopy from 10 up to 4000 cm⁻¹. The polarized infrared (IR) reflectivity spectra were measured between 7 and 250 K, in the frequency range 10–600 cm⁻¹. From the IR spectral analysis, the phonon modes were classified within their symmetry species, and their longitudinal (LO) and transversal (TO) optical frequencies were calculated. A tentative assignment of the various internal modes observed in the transmissivity spectrum of LHP, between 300 and 4000 cm⁻¹, is proposed. The present study did not reveal any low-temperature structural phase transition.     

Experimental and theoretical study of the IR absorption spectrum of 2,4-oxazolidinedione

The IR absorption spectra of 2,4-oxazolidinedione in tablet and solution form were measured over the frequency range 400–3600 cm^–1. The complete set of normal modes for the molecule are calculated on the basis of a mechanical model with symmetry C_s. The spectrum is interpreted. The spectral features can be explained by taking into account the strict C_s symmetry of the molecule as a whole and the approximate C_2v symmetry with traces of D_5h for the ring.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 27–32, September, 1970.     

Anharmonic resonances in the vibrational spectra of pyrazine

The quartic force field of pyrazine has been calculated in the B3LYP/6-31G(d) hybrid density-functional approximation. Based on the results of this calculation, the total IR (250–3800 cm^–1) and Raman (400–3200 cm^–1) spectra of pyrazine have been interpreted with consideration for the Fermi and Darling-Dennison resonances and their spectral manifestations. A precision method is proposed for anharmonic analysis of the vibrational states of polyatomic molecules on the basis of consideration of their theoretical anharmonicity constants in combination with the corresponding experimental frequencies. The method of linear scaling of frequencies has been theoretically substantiated.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 13–22, January–February, 2005.     

Analysis of the Structure of the Bands in the IR Spectrum of β-D Glucose by the Regularized Method of Deconvolution

Deconvolution of the IR absorption spectrum of -D glucose in the spectral range 1500–450 cm^–1 has been carried out. The results of the deconvolution were compared with the IR and Raman spectra recorded at room and low temperatures and with the data obtained by theoretical calculations for the frequencies of the normal vibrations of the -D glucose molecule in the crystalline state. It is shown that deconvolution of the IR spectra recorded at room temperature makes it possible to separate the bands observed experimentally only at a very low temperature of the sample and a number of components that were not resolved earlier. The number of bands separated on deconvolution of the IR spectra of -D glucose in the spectral range 1500–450 cm^–1 is more than twice the number of visible absorption maxima in the usual spectrum. The results of deconvolution of the IR spectrum of -D glucose are in good agreement with the data of theoretical calculations for the frequencies of the normal vibrations of the -D glucose molecule in the crystalline state. The existence of the factor-group (Davydov) splitting of a number of frequencies of the nondegenerate fundamental vibrations of molecules in a crystal cell has been revealed in the IR spectrum of -D glucose. It was concluded that the model of an isolated molecule is insufficient for detailed theoretical interpretation of the vibrational spectra of carbohydrates.     

Role of Intermolecular Interactions in Forming the Vibrational Spectra of Carbohydrate Nitrate Crystals in the Region 1600–1700 cm−1

To elucidate the role of intermolecular interactions in forming the vibrational spectra of the crystals of carbohydrate nitrates in the region 1600–1700 cm^–1, theoretical calculations are performed (in the approximation of an additive model of interatomic interactions with the use of the Green's functions) for the density of vibrational states and the intensity of absorption bands in the IR spectrum of a methyl--D-glucopyranoside tetranitrate molecule in a crystal. It is shown that the splitting of absorption bands in the IR spectral region under consideration relates to the crystal effect.     

Thermal annealing of defects in irradiated zinc oxide

The change with thermal annealing of the diffuse-reflection and luminescence spectra of electron irradiated polycrystalline zinc oxide was investigated. It was found that the absorption band of F^– and F^±centers increased at T<543°K and decreased at high temperatures. The change in the parameters of the exciton luminescence bands correlates with the change of absorption in the F^– and F^±bands. Absorption in the band of interstitial zinc ions decreases over the whole range of annealing temperatures. The effect of thermal annealing on the absorption in the near IR range of the spectrum was investigated. Explanation is given of the regularities established.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 60–65, September, 1985.     

Influence of Iodine-Containing Solutions on the Condition of a Porous Silicon Surface and Its Photoluminescent Properties

The influence of surface treatment of porous silicon in iodine-containing solutions on its photoluminescent properties has been investigated. The porous silicon samples were prepared by anodizing in HF-based electrolytes and placed in fluoride-hydrogen solutions with the addition of iodine immediately after their formation. The surface condition was controlled by IR Fourier spectroscopy methods in the 400–4000-cm^–1 range. It has been established that the result of the porous silicon treatment in iodine-containing solutions is a decrease in the intensity of Si–H _x -bonds without the appearance of additional vibrations in the range under investigation. At the same time, such a treatment substantially affects the spectrum and intensity of porous silicon photoluminescence and increases its stability in subsequent storage. The possible reasons for the revealed phenomena are discussed.     

Temperature dependence of IR band strength for polyethylene

IR spectra at 150° K and detailed temperature curves for 150–310° K for the 965, 985, 1175, 1890, and 2010 cm^–1 bands are reported. The background bears a direct relation to temperature, whereas the bands have a negative temperature coefficient of intensity. The weakening of the 944 cm^–1 band is irreversible.     

Characteristic bands of the valence vibrations of the NO2 group in infrared absorption spectra. Part 1. Experimental data and band assignments

Frequency and intensity (integral and peak) are given for bands in the IR absorption spectra of 71 nitrocompounds; these are assigned to the symmetric valence vibration (1300–1400 cm^–1) of the C-NO₂ group and to the antisymmetric one (1500–1600 cm^–1). The splitting of the symmetric band is discussed in relation to resonance in the coupled vibrations of the nitro and methyl groups in saturated nitro-compounds.     

Use of infrared absorption spectra for studying the conformational equilibrium of cis-1-methyl-2-ethylcyclohexane

The equilibrium of the three most stable conformations of cis-1-methyl-2-ethylcyclohexane has been examined on the basis of changes in intensity of the triplet at 585–610 cm^–1 in its infrared absorption spectrum on changing the temperature from 30° to –140° C. H and S have been determined.     

An IR-Radiometer with Internal Signal Modulation

An infrared (IR) radiometer electrical circuit on the basis of photoresistors and photodiodes made of silicon doped with zinc (Si) as well as the narrow bandgap semiconductor alloy Pb_0.78Sn_0.22Te is presented. In the circuit suggested a bridge with the photoreceiver connected to the radiometer input and immediately fed by signal generators functions as a radiation modulator. The threshold sensitivity turned out on a recorder is 2·10^–13 W·Hz^–1/2 (for the n⁺–n–n⁺ structures made of Si, =0.8–l.2m, T=300K); 1.4·10^–15W·Hz^–1/2 (for p⁺–n–n⁺ S-diodes on the basis of Si, =0.8–1.2m, T=300K) and 10^–12W·Hz^1/2 (for photodiodes on the basis of Pb_0.78Sn_0.22Te, =8–13m, T=77K).     

Development of a tunable IR lidar system

A differential absorption lidar system (DIAL) based on a continuously tunable optical parametric amplifier (OPA) pumped by a Nd : YAG laser (200 mJ at λ=355 nm) operating at a maximum pulse repetition rate of 100 Hz has been developed. The system provides continuously tunable coherent radiation in the Visible–near IR range (0.4–2.5 μm), allowing to perform DIAL measurements in a spectral region where most of atmospheric constituents and pollutants display absorption lines. The spectral width of the OPA system is line-narrowed by using a master oscillator dye laser as seeder, achieving a linewidth of 0.04 cm⁻¹ (FWHM), a spectral purity larger than 99% and a frequency stability better than 1 pm h⁻¹, with an output energy in the IR of 1–10 mJ. The OPA system was used to perform DIAL measurements in the lower troposphere. Preliminary results in terms of water vapor content and aerosol backscattering profiles are presented and discussed.     

Evolution of the Electroluminescence Spectra and the Acoustic Emission of the Epitaxial Structures of GaAsP

The dependence of the spectral position of the electroluminescence bands of epitaxial light-emitting diode n ⁺–n–p structures (GaAs_0.15P_0.85) on the density of a direct heterojunction current at different successive instants of time — before an acoustic emission and after it — has been revealed. The shifts of the electroluminescence bands accompanied by acoustic emission can be divided into three types according to the density of the current: (1) short-term shifts due to relaxation of the defect structure of a sample — at relatively low currents, (2) the magnitude of the reverse shift being determined by the current density — at large currents, and (3) formation of an IR band (1.5–1.1 eV) with irreversible degradation changing in the red (1.75 eV) and green (2.19 eV) bands of the electroluminescence spectrum — at ultrahigh currents (100–200 A/cm²).     

Infrared absorption spectra of some monosubstituted benz-2,1,3-thiadiazoles

The IR spectra in the 500–1900 and 2800–3200 cm^–1 regions were recorded for six compounds: 4- and 5-methyl-, 4- and 5-chloro-, and 4- and 5-bromobenz-2,1,3-thiadiazoles. An assignment is given for some of the bands.Translated from Izvestiya VUZ. Fizika, Vol. 11, No. 8, pp. 18–22, August, 1968.