L. E. Semenova

Hyper-Raman scattering by 2LO-phonons in a CdS crystal

A theoretical treatment of the resonant hyper-Raman scattering (RHRS) of light by 2LO-phonons is presented for a CdS crystal. The scattering mechanisms of the RHRS by 1LO- and 2LO-phonons are considered. The corresponding efficiencies are compared.

Hyper-Raman scattering of light: forbidden scattering mechanisms

Theory of the resonant hyper-Raman scattering (RHRS) of light by the longitudinal optical phonons in semiconductors is developed. It was shown that the forbidden scattering mechanisms can result in features of the RHRS intensity frequency dependence under resonant conditions.

Theoretical investigation of the resonant hyper-Raman scattering by optical phonons

A theoretical model for the resonant hyper-Raman scattering in semiconductor crystals is presented. The Wannier excitons are considered as intermediate states. The expressions for the resonant hyper-Raman scattering cross section are obtained. The theoretical model developed allows taking into account different mechanisms of the exciton-photon and exciton-phonon interactions.

Resonant hyper-Raman scattering of light in semiconductor crystals: Froehlich exciton-lattice interaction

Theory of the resonant hyper-Raman scattering of light by the longitudinal optical phonons in semiconductors which include excitonic effects has been developed. The theory can be applied at double frequency of incident radiation below and above the band gap. The matrix elements corresponding to the transition between different exciton states are calculated analytically. The contributions of the discrete and continuous states to the hyper-Raman intensity are compared.

Theoretical treatment of the resonant hyper-Raman scattering in A2B6 semiconductors

In this work the theoretical treatment of the hyper-Raman scattering of light by LO-phonons is given for A2B6 semiconductors of the wurtzite structure, taking into account the influence of the complex top valence band which consists of the three closely-lying subbands.

The treatment of the hyper-Raman scattering by 2LO phonons in semiconductors with equal effective masses of electrons and holes

The theoretical investigation of the hyper-Raman scattering by 2LO phonons is carried when the doubled energy of incident photons lies near the band gap of a semiconductor. The scattering process is considered, taking into account the Wannier excitons as intermediate states.

Raman study of deformation of polyethylene

Oriented polycrystalline polymers with high mechanical properties are very important for many practical applications. Such materials can be produced by drawing at temperatures near to their melting point. During the drawing process, macromolecules are aligned along the drawing direction, which leads to a considerable increase in the Youngs modulus, strength and stiffness of polymer. The orientation distribution function of macromolecules is one of the most significant characteristics of the structure of oriented polycrystalline polymers. The coefficients of the distribution function expansion in a series of generalised spherical harmonics can be determined by several techniques, such as X-ray analysis, IR-spectroscopy, and birefringence measurements. Raman spectroscopy is one of the most convenient and informative tools for studying the orientation of macromolecules. It has been shown that Raman spectroscopy is capable of determining the expansion coefficients up to the fourth order for both crystalline and amorphous phases [1,2]. At present, Raman spectroscopy is often used to study the orientational order in a various polycrystalline polymers (see references from [3]). Here we present the investigation of mechanism of uniaxial deformation of polyethylene from the isotropic state to the extremely drawn state (when increasing the draw ratio causes the sample to break apart).