We present a calculation of the dielectric correlation function in glasses showing how the assumption of short correlation length for normal modes breaks the momentum selection rules and leads to expressions for the first-order Raman-scattering intensity in terms of the density-of-states functions and known frequency-dependent amplitudes.

This work is concerned with ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ -based compounds known as being highly effective materials for thermoelectric applications near room temperature. These compounds are characterized by a remarkable anisotropy linked to their $R\overline{3}m$ crystal structure. Two textured $p$ -type ${\mathrm{Bi}}_{0.4}{\mathrm{Sb}}_{1.6}{\mathrm{Te}}_3$ samples were prepared using a powder metallurgy approach, with the $c$ axis parallel to the pressing direction. One sample was undoped while the second was doped with Pb which acts as an acceptor. The electrical conductivity, Hall coefficient, and magnetoresistivity were measured from room temperature down to $6\mathrm{K}$ . The Seebeck coefficient $\alpha$ and electrical conductivity $\sigma$ were measured along and perpendicular to the $c$ axis from 300 up to $550\mathrm{K}$ , and the thermal conductivity $\kappa$ was measured at $300\mathrm{K}$ . Different values of Seebeck coefficient were observed along and perpendicular to the $c$ axis at temperatures above $T_i$ , the beginning of intrinsic region in which the influence of the minority carriers becomes significant. Below $T_i$ , the Seebeck coefficient was isotropic. The maximal power factor $P={\alpha }^2\sigma$ , calculated on the basis of the experimental results, was about $40\mu \mathrm{W}{\mathrm{cm}}^{-1}{\mathrm{K}}^{-2}$ for the direction perpendicular to the $c$ axis. The thermal conductivity values for the temperature domain above $300\mathrm{K}$ were calculated on the basis of a physical model and the measured values at $300\mathrm{K}$ . The calculated values of the figure of merit $Z=P∕\kappa$ were $3\times {10}^{-3}$ and $2\times {10}^{-3}{\mathrm{K}}^{-1}$ at 300 and $400\mathrm{K}$ for the two samples, respectively. These values are comparable to those observed in ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ -based single crystals, thus making the powder metallurgy approach appropriate for thermoelectric conversion applications.

The $L_2$,3 emission spectrum of c-Si, excited by monochromatized synchrotron radiation, has been recorded with a 5-m Rowland spectrometer. Dramatic spectral changes are observed as the excitation energy is varied from the 2p binding energy up to 144 eV. It is proposed that a spectator electron, close to the bottom of the conduction band, influences the emission spectrum. The observations suggest that intraband shakeup is important in the excitation process, and that a population of low-lying levels, via initial-state shakeup, influences the high-energy-excited Si L emission spectrum.

Pulsed resonant optogalvanic effect is investigated in a neon hollow cathode discharges utilizing a nitrogen pumped dye laser. We have studied by the pulsed technique transient effects in the discharge plasma such as fast relaxation of level population density and population inversion. The experimental results are correlated with a four states phenomenological model of the pulsed optogalvanic effect taking into account lumped relevant levels of the 3s and 3p manifolds of neon. The time integration of the pulsed optogalvanic siganls (OGS) yields the previously measured cw signals and explains their sign changes.

The theory of Raman scattering from the vibrations of amorphous materials is applied to the spectra of B₂O₃ glass and its melt. Experimental evidence is obtained indicating that low frequency scattering in the melt liquid is also due to first order scattering from intermolecular vibrational states. The relationship among several scattering mechanisms in liquids is discussed.