Spectrum Of Vibrational Modes Research Articles

Raman spectra of vibrational modes in spinel CdIn2S4

AbstractWe here present the results of a Raman investigation on powders and oriented single crysstals of CdIn2S4 spinel, nominally pure and doped with Fe.The k  0 fundamental phonon frequencies are: 184 cm−1 (Eg), 242 cm−1 (F2g), 307 cm−1 (F2g) and 362 cm−1 (A1g). An additional first order vibration, which is ascribed to a local mode of Fe in tetrahedral sulphur surroundings, is found at 340 cm−1 and has A1g‐symmetry.

Fundamental Research on Gear Noise and Vibration : 7th Report, Generation Mechanism of Radial and Axial Vibration of Spur Gears-II

In this report, various kinds of vibrations of a gearing, including those of bearings, are examined closely on their phase-relationship, vibrational mode and frequency spectrum, whose results are compared with the calculated ones based on the theory in the 6th report. Results obtained are as follows : The theory is useful not only for behaviours and the vibrational mode of the circumferential vibration and the radial one in spur gears but also for the vibrational mode of bearings, although the calculated value for the conversion ratio to radial vibration is a little smaller than the experimental one mainly because of the frequency characteristics of bearings being neglected. Regarding the generation mechanism of the axial vibration of spurgears, the vibration of a gear body as an elastic circular disc, which was not considered in the theory, can be predominant by a resonance under some definite condition.

Localized vibrational modes of Li defect complexes in GaAs

Li defects created in GaAs by high-temperature Li diffusion were studied via their IR-active localized vibrational modes. In an exploratory series of experiments the effects of varying the Li diffusion conditions on the localized vibrational mode spectrum were studied. The variables included (i) the diffusion temperature, (ii) initial doping of the GaAs, and (iii) the Li isotope in a series of sequential high- and low-temperature diffusions. It was concluded that the Li defects consist of Li complexed with native defects created during the diffusion heat treatment and stabilized by the Li. Detailed measurement and analysis of spectra due to Li isotope mixtures yielded the numbers of Li atoms/complex and Li site equivalences.

Surface Modes of Vibration in the Rigid-Ion Model of NaCl

A discussion is given of the complete spectrum of vibrational surface modes for the Kellermann rigid-ion model of NaCl. The attenuation with distance from the surface is shown for representative surface and pseudosurface modes. We discuss one interesting feature which has not previously been pointed out: Symmetry requirements can lead to surface modes which are associated with only one species of ion (${\mathrm{Na}}^{+}$ or ${\mathrm{Cl}}^{\ensuremath{-}}$) at the surface.

Surface Lattice Dynamics of Silver. II. Low-Energy Electron Thermal Diffuse Scattering

Intensity measurements of the diffracted current in the low-energy electron diffraction from the (111) surface of silver show broad wings associated with the Bragg peaks. These wings have been identified as the thermal diffuse scattering. The observed intensity has been compared with model calculations for kinematic scattering of nonpenetrating radiation, using a Debye spectrum of vibrational modes. After the effects of the scattering factor and a temperature-independent background are accounted for, the data agree with the predictions of the model in the following ways: (i) Throughout nearly the entire Brillouin zone the intensity was inversely proportional to the distance to the nearest reciprocal-lattice rod. (ii) The ratio of the diffuse intensity to the peak intensity was proportional to temperature. (iii) The same ratio was proportional to the square of the length of the scattering vector. (iv) The ratio of the integrated intensities in the thermal diffuse scattering and in the peak was approximately equal to the exponent in the Debye-Waller factor. Refinements of the model to include qualitatively the penetration of the incident electrons and the free-surface elastic boundary conditions yield additional features that are only suggested in the data. However, to within the uncertainties in this analysis and the experiments, the results for the close-packed surface of silver can be understood in terms of an elastic continuum, and are consistent with the Debye-Waller factor for low-energy electrons.

THEORY OF THE DYNAMICAL JAHN-TELLER EFFECT IN STRONG COUPLING

The dynamical Jahn-Teller effect has been treated in the case of strong coupling for which the static distortional energy of electrons is larger than the energy of a typical vibrational quantum. A perturbation method which applies to strong coupling is developed. The eigenfunction and eigenvalue are expanded as power series of the ratio of the vibrational quantum to the static distortional energy. We have dealt explicitly with the Jahn-Teller effect of the Г8 state of an Oh point group; the energy levels of electronic-vibration system are obtained. The characteristics of strong coupling as compared with weak coupling are: 1) although no static distortion actually appears, the degeneracy and frequency spectra of vibrational modes are changed; 2) the collective modes of electronic-vibration system will appear, if the vibrational modes coupled to the electrons are "tuned". The theory is employed to interpret the experimental results obtained by Weinstock et al. on TcF6 and ReF6 from the infra-red and Raman spectra.