Low-frequency spectroscopy of four-photon scattering of laser radiation in aqueous solutions of biopolymers

Four-photon scattering (FPS) spectroscopy is used to record rotational resonances of H₂O and H₂O₂ molecules in aqueous solutions of DNA and denatured DNA within a range of ±10 cm^-1 with a spectral resolution of 3 GHz. The resonance contribution of rotational transitions of these molecules in solutions was found to be considerably larger than that in distilled water. This fact is interpreted as a manifestation of the specific properties of a hydrate layer at the interface between water and DNA or denatured DNA molecules. An analysis of the FPS spectra shows that the concentration of H₂O₂ molecules in the hydrate layer of the DNA molecule increases threefold after denaturation. In addition, the FPS spectra of aqueous solutions of α-chymotrypsin protein with concentrations of 0-20 mg cm^-3 were measured in the spectral range of ±7 cm^-1. It is found that the velocity of hypersound in the protein aqueous solution, which is measured by the shift of the Mandelstam—Brillouin scattering spectrum components, is a cubic function of the concentration and reaches 3000 m/s at 20 mg/cm³.     

Infrared Spectra of Water in Aqueous Solutions Using Internal Reflection Spectroscopy

Abstract

There has been a continuing interest in the structure of water and of aqueous solutions, and many studies have employed spectroscopic techniques. These have frequently involved absorption spectroscopy in the near-IR range, and Raman scattering. In general, however, the normal IR range has been but little used except for studies of HDO-containing solutions, and the region near 3500 cm^?1 of the intense H₂O absorption has been almost completely avoided. Transmission techniques have been exclusively employed with absorption spectroscopy. Internal reflection spectroscopy (IRS) techniques have been employed to examine aqueous solutions, but the emphasis was placed on studying the solute rather than the solvent. Also, the solute concentrations which had been employed in transmission studies have been rather high. We now suggest the feasibility of carrying out structural studies of aqueous solutions by using IRS techniques to record spectra in the IR range, employing solutions of relatively low concentrations. For example, the lowest concentration of aqueous HCl solution examined by Ackermann¹ was 2.5 M by transmission techniques in the 4000-1100 cm^?1 range; in contrast, using IRS, the perturbations of the O-H stretching and deformation bands of H₂O could be observed with 0.1 M HCl.     

Concentration dependence of the intermediate frequency bandwidth of submillimeter heterodyne AlGaAs/GaAs nanostructures

The concentration dependence of the intermediate frequency bandwidth of heterodyne AlGaAs/GaAs detectors with 2D electron gas is measured using submillimeter spectroscopy with high time resolution at T= 4.2 K. The intermediate frequency bandwidth f_3dBfalls from 245 to 145 MHz with increasing concentration of 2D electrons n _s = (1.6-6.6) × 10[su11] cm^-2. The dependence f_3dB ≈ n _s ^- 0.04±is observed in the studied concentration range; this dependence is determined by electron scattering by the deformation potential of acoustic phonons and piezoelectric scattering.     

Bimodal dependence of light scattering/fluctuations on the concentration of aqueous solutions

Two concentration ranges (from 10^?5 to 10^?9 and from 10^?13 to 10^?18 M) corresponding to enhanced fluctuations of Rayleigh and Raman scattering of second-harmonic (527 nm) pulses of YVO₄:Nd³⁺ laser are found for aqueous solutions of antioxidant potassium phenosan. A correlation is revealed between the rise in elastic Rayleigh scattering intensity and its fluctuations and the shift of the center of OH Raman band of water toward the ice component characteristic frequency (3200 cm^?1). The development of phase-equilibrium instabilities is analyzed based on the model of fluctuations of the number of hydrogen bonds on the assumption of formation/destruction of ordered hydration layer of phenosan molecules in water.     

Ammonium dynamics in the disorder a-phase of K1- x (NH4) x Y (Y=Cl,Br, I). a neutron scattering study

Temperature and concentration effects on the lattice parameters and the amplitude weighted phonon density of states (AWPDS) in the mixed salts of ammonium-potassium halides were investigated by neutron powder diffraction (NPD) and incoherent inelastic scattering (IINS). In the disorder α-phase (NaCl type), ammonium ions perform a fast stochastic reorientation at phonon frequencies rate, down to ca. 80 K. The IINS spectra at 10 K displayed the four distinct ammonium excitations, two (resonant) modes below and two (localised) above the cut-off frequency of the AWPDS of potassium halides. The high frequency localised modes correspond to the translational and librational vibrations of NH₄ ions. These modes are typical for ordered phases of ammonium halides. Ammonium concentration effects on the localised and resonant modes were studied for the K_{1? x} (NH₄) _x I mixed salts and the harmonic excitations of ammonium in the hypothetical low temperature α-phase of NH₄I were approximated to ca. 30, 95, 155 and 250 cm^?1. In the real low temperature ordered γ-phase of NH₄I, translational ammonium vibrations were observed at ca. 140-160 cm^?1 and librational at ca. 300 cm^?1.     

Spin relaxation of conduction electrons in highly-doped n-type germanium at low temperature

We present a theory of the spin relaxation time of the conduction electrons in highly-doped n-type germanium at liquid helium temperature. The theory is compared with some of our measurements and the experimental data available in the literature on As-doped germanium. The observed linewidth at T = 10 K is accounted for in the whole metallic concentration range (N_D > 3 × 10¹⁷cm^?3).In the lower concentration range (3 × 10¹⁷ < N_D < 10¹⁸cm^?3), the relevant mechanism is the random jumping of the g factor upon intervalley scattering. The agreement with experiment is good without any adjustable parameter.In the higher concentration range (N_D > 10¹⁸cm^?3), the dominant process for the linewidth is the spin-flip scattering by ionized donors (Elliott process); the usual theory is shown to be insufficient and the greater effectiveness of scattering by the localized part of the donor potentials is pointed out. The calculated linewidth is related to the intervalley scattering time T_iv. The agreement with experiment is good and predictions are given for the linewidth in the case of other shallow donors in the same concentration range.     

Light scattering by magnetic excitons in (FeMn)F2

The transitions between the low lying crystal field split states A_1g and B_1g of the Fe²⁺ ions in pure FeF₂ and in the mixed antiferromagnet Fe_1-xMn_xF₂ have been investigated with Raman light scattering. From the Raman polarization rules the lines have been identified as arising from the magnetic excitons associated with the transitions. The energy and the line-width of the strongest line are studied as a function of the concentration x. From the energy measurement we estimate that the single ion anisotropy parameter D of the Fe²⁺ ions varies from 6.46 cm^-1 in pure FeF₂ to 8.03 cm^-1 in MnF₂: Fe.     

Raman scattering by optical phonons and polaritons in CuCl

We present data on forward and backward scattering in CuCl at liquid N₂ temperature. Peaks at 146 and 172 cm^-1 which appear in both forward and backward scattering spectra are attributed to other than first order scattering by optical phonons. The data on polarition scattering indicate that the atomic displacement contribution to the scattering by TO phonons is rather small. From the experimentally determined polarition dispersion curve we obtain a value of 174 ±2.5 cm^-1 for ω_T and a value of 5.3 for ?_S.     

Thermal stability and radiation hardness of SiC-based schottky-barrier diodes

Pt/W/Cr/SiC Schottky-barrier diodes that retain good electrophysical parameters up to 450°C are studied. With the Auger electron spectroscopy (AES) method, it is shown that the thermal stability is provided by using a multilayer metal composition that ensures the metal/SiC interface stability. The surface-barrier structures obtained are tested for radiation hardness. They are irradiated by fast neutrons with a fluence of 4.42×10¹⁵ n/cm² and attendant γ radiation with a dose of 8.67×10⁵ R in the concentration range of N _d-N _a=10¹⁶−5×10¹⁷ cm⁻³. Irreversible modifications of the structures at N _d-N _a≤8×10¹⁶ cm⁻³ are found. The degradation of the parameters is inversely proportional to the doping level.     

RAMAN STUDY ON (Pb) CENTERS IN SINGLE CRYSTALS OF ALKALI HALIDES DOPED WITH LEAD

Low frequency modes were observed in a series of alkali halides doped with lead after X-irradiation at 77K. The peak positions of the Raman signals are at 34cm^-1 for NaCl:Pb²⁺, 30cm^-1 for KCl:Pb²⁺,28cm^-1 for RbCl:Pb²⁺ and 22cm^-1 for KBr:Pb²⁺. They are assigned to the inelastic light scattering caused by the local vibration of X^-_i (Pb⁺) center, which consists of an interstitial halogen ion stabilized by a substitutional ion Pb⁺ . Polarized Raman measurements and Behavior Typer(BT) analysis show that the symmetry of the X^-_i (Pb⁺) center belongs to the point group C_3v A structure model of the X^-_i (Pb⁺) center is proposed based on the Raman data and the result of BT analysis.     

A Raman scattering study of long-wavelength optical phonons in hexagonal ammonium fluoride single crystals

All the predicted Raman active translatory vibrations of wurtzite ammonium fluoride (space group C⁴_6v are observed and assigned on the basis of their polarization selections obtained with single crystals. The fundamental ammonium ion librations could not be detected, but a frequency of about 545 cm^?1 is deduced from the analysis of the observed second order Raman spectrum.The TO-LO splitting for the A₁ and E₁ polar phonons is a lot more important than the A₁ — E₁ splitting (125 cm^?1 compared to 1–3 cm^?1); thus, the effect of long-range electric forces strongly dominates over that of the anisotropy of the shortrange interatomic forces. Only very weak directional dispersion could be detected on the quasi-mode spectra. From the observed TO and LO frequencies, one evaluates ?₀ ? 3.95 in good agreement with dielectric experimental data.     

Ag偏离化学计量比Ag1－xPb18SbTe20材料的热电传输性能

采用熔融-淬火-放电等离子体烧结制备了Ag偏离化学计量比Ag_1-xPb₁₈SbTe₂₀(x=0，0.25，0.50，0.75)样品，研究了Ag含量对样品热电传输性能的影响.结果表明，随Ag含量降低，样品中出现少量第二相Sb₂Te₃，样品载流子浓度增加到5×10¹⁸cm^-3后不再增加.样品载流子迁移率随Ag含量降低先降低后增加，随着温度增加，载流子散射机理由电离杂质散射转变为声学波散射.随Ag含量降低，样品电导率增加而Seebeck系数降低，热导率增加. 关键词： 热电材料 mSbTe_m+2')" href="#">AgPb_mSbTe_m+2 SPS 散射机理     

Dynamics of liquid ammonia from cold neutron scattering

The scattering of 4.1 Å neutrons by liquid ammonia has been measured at 218 K in the angular range of 30–90° using the Trombay rotating crystal spectrometer. The experimental data, after correcting for multiple scattering, have been compared with model calculations, and it is shown that it is possible to get detailed information about the rotational correlation function on the basis of neutron experiments alone. The model assumes Langevin diffusion for translational motions. Rotational motions are described by means of an orientational correlation function which has a gaseous behaviour for times up toτ ₀ and then changes over to a diffusive character with a rotational diffusion constantD _r. Within the framework of the model the correlation function can be described withD _r=0.28×10¹³sec^?1 andτ ₀=0.57×10^?18sec. Corrections for multiple scattering and their dependence on model parameters are discussed.     

Incoherent quasielastic neutron scattering from H2O and aqueous ZnCl2 solutions

A study of the diffusive motions of the protons in pure water and ZnCl₂ aqueous solutions has been performed, using incoherent quasielastic neutron scattering. It is shown that it is essential to take into account the rotational motion of the water molecules. The translational linewidth is conveniently fitted over the whole Q-range, using the Random Jump Diffusion model for which the jump length turns out to be roughly the same for pure H₂O and the saturated solution, fairly close to the distance between protons in the water molecule.     

High pressure cyanide exchange study on a square-planar tetracyanometalate complex of Pt(II)

Abstract

Previous studies of cyanide exchange on square planar tetracyanoplatinate complex [Pt(CN)₄]^2- have been undertaken only at a high pH. For a more complete fundamental understanding of this system we extended the investigations of these exchanges over a large pH range. NMR kinetics methods (magnetisation transfer, isotopic exchange) proved to be very useful for obtaining quantitative rate data of the cyanide exchange on this complex. In fact it is quite significant that the reactivity of this metal center spans a ca. 9-order of magnitude range as a function of pH.

Variable temperature and variable pressure studies were undertaken in aqueous solutions and the following activation parameters obtained: ΔH? = (25.1 ± 0.4) kJmol^?1 and activation entropy ΔS? = -(142±2)JK^?1mol^?1 and activation volume ΔV? = -(27±2)cm³mol^?1.     

Spectroscopy of phonon and vibronic states of YbAl3(BO3)4 single crystal

The polarized Raman and reflection spectra of a single crystal YbAl₃(BO₃)₄ at room temperature were studied. Raman active vibrational modes A ₁, E _TO, and E _LO are identified. In the Raman spectrum, we detected an intense line at a frequency of 1018 cm⁻¹, which refers to internal vibrations of the BO₃ group and is known to be promising for use in amplifiers based on stimulated Raman scattering. From the simulation of reflection spectra by the method of dispersion analysis the frequencies of A ₂ vibrational modes were determined. Intense bands observed in the low-temperature transmission spectra in the range of f-f transitions in the Yb³⁺ ion are attributed to electron-phonon transitions. The Raman lines are compared with electron-phonon lines in the transmission spectrum.     

Die Eigenschwingungen des Metall-Hydratkomplexes in BeSO4·4H2O und BeSO4·4D2O

Infrared reflection spectra of single crystals of BeSO₄·4H₂O and BeSO₄·4D₂O have been obtained in polarized light at 300°K and at 14°K in the region between 4000 cm^?1 and 300 cm^?1. By a Kronig-Kramers analysis, the frequencies of the infrared active transitions have been calculated. These transitions are attributed to internal vibrations of the water molecules and sulfate ions and, in the region between 1000 cm^?1 and 300 cm^?1, especially to internal and external vibrations of the tetrahedral Be⁺⁺·4aqu-complexes. The vibrational modes of these complexes consist of a superposition of translational and librational modes of the water molecules and translational modes of the central Be⁺⁺-ion. The vibrational frequencies and normal modes of this complex have been calculated in a central-force model, and force-constants have been determined by fitting the calculated frequencies to the observed spectra. The calculations have shown that the modes, which comprise mainly translational motions of the water molecules, are strongly coupled with librational motions of the water molecules. On the other hand, there exist pure librational modes with practically no admixture of translational motions. The optimum sets of force constants for the BeSO₄·4H₂O crystal and the BeSO₄·4D₂O crystal differ in a manner which can be understood under the assumption that the dimensions of the Be(D₂O)₄ complex are about 0.1 Å larger than those of the Be(H₂O)₄ complex. Some arguments supporting this conclusion will be discussed.     

Far-infrared quasi-local modes of ZnTe in CdTe

We report the very far-infrared absorption spectra of the mixed-crystals Cd_1-xZn_xTe for small x in the temperature range of 4.2K–150K and the wavenumber region of 20cm⁻¹–100cm⁻¹. The quasi-local mode induced by ZnTe in CdTe and CdTe-like 2TA two-phonon creations are observed, to be best of our knowledge, for the first time. The frequencies of the modes are estimated by using the mass-defect model combined with Green's functions calculations. Besides, the temperature dependence of the absorption peak is well explained in the light of the characteristics of the modes.     

Scattering mechanisms of charge carriers in transparent conducting oxide films

Scattering mechanisms of charge carriers in Transparent Conducting Oxide (TCO) films have been analyzed theoretically. For the degenerate polycrystalline TCO films with relatively large crystallite sizes and high carrier concentrations (higher than 5 × 10¹⁸ cm^–3), the depletion layers between crystallites are very thin compared to the crystallite sizes, and the grain boundary scattering on electrical carriers makes a small contribution to limit the mobility of the films. Instead of thermionic emission current, a tunneling current dominates the electron transport over grain boundaries. The Petritz model which is based on thermionic emission and extensively quoted in literature should not be applicable. The main scattering mechanisms for the TCO films are ionized impurity scattering in the low-temperature range and lattice vibration scattering in the high-temperature range. The ionized impurity scattering mobility is independent of temperature and the mobility due to thermal lattice vibration scattering is inversely proportional to the temperature. The results obtained from Hall measurements on our ZnO, ITO, SnO₂ and SnO₂:F films prepared with various methods supports the analysis.     

A Raman scattering study of the phase transition in the (NH4)3WO3F3 oxyfluoride

The Raman scattering spectra of polycrystalline samples of the (NH₄)₃WO₃F₃ perovskite-like oxyfluoride were measured at frequencies of 70–3600 cm^?1 in the temperature range 93–323 K, including the transition from the orientationally disordered cubic phase to the low-symmetry phase. Transitional anomalies in the spectral parameters were revealed in the frequency ranges of internal vibrations of the ammonium ions and WO₃F₃ octahedral groups. An analysis of the experimental results allowed the conclusion that the phase transition under study is associated primarily with the ordering of the octahedral groups.