Inelastic light scattering in the Eu chalcogenides and in YbTe

First-order inelastic light scattering exhibiting broad linewidths and multiphonon lines has been measured in the magnetically ordering EuO, EuSe, and EuTe as well as in the diamagnetic YbTe. Whereas the light scattering of EuSe is similar to that of the earlier investigated EuS, we find that EuO, EuTe, and YbTe exhibit in part an anomalous behaviour. We conclude, that the inelastic broad-line light scattering found in these compounds cannot be explained by Raman theory. Instead, we suggest that this light scattering is better characterized by a recombination process.     

Inelastic light scattering in highly excited GaAs

The coupled plasmon-LO-phonon and single-particle excitations of a photocreated electron-hole plasma in high purity GaAs are studied by means of Raman scattering measurements. The experimental results are described by the random-phase approximation with respect to the multicomponent character of optical plasma. From single-particle spectra the plasma distribution function and drift velocities up to 10⁷ cm/s have been determined. Using the coupled modes as probe for the plasma density the temperature dependence of the recombination in the EHP is studied.     

Inelastic light scattering in magnetic dots and wires

An overview of the current status of the study of spin-wave excitations in arrays of magnetic dots and wires is given. We describe both the status of theory and recent inelastic light scattering experiments addressing the three most important issues: the modification of magnetic properties by patterning due to shape anisotropies, anisotropic coupling between magnetic islands, and the quantization of spin waves due to the in-plane confinement of spin waves in islands.     

Inelastic light scattering by dipolar excitons

The cross section for inelastic light scattering by a system of spatially indirect excitons is calculated. It is shown that there are two resonant scattering channels, one related to the transitions via the vacuum and the other via the two-exciton states of the crystal, and their contributions to the scattering amplitude cancel each other. As a result, there is no resonance enhancement of light scattering by excitons for photon energies in the vicinity of the band gap.     

Inelastic light scattering by electrons and plasmons in metals

The cross section of the inelastic light scattering by electron-hole plasma in metals is studied. The Coulomb interaction of electron excitations is taken into account self-consistently. The system of the Boltzmann equation for electronic fluctuations and Maxwell’s equations for the interaction field is solved. The Raman spectra consist of the electron-hole background, diffuson and plasmon resonances. The widths of this background and resonance are determined by the electron collision rate as well as by the decay of the incident and scattered radiation in the metal. The line shape depends on the screening of the electron-light interaction, i.e., on the incident radiation frequency. Zh. éksp. Teor. Fiz. 112, 679–689 (August 1997) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Inelastic light scattering in hole-accumulation layers on silicon

Hole-accumulation layers on silicon (100) are studied using resonant inelastic light scattering techniques. The observed intersubband transitions are in good agreement with Hartree calculations of Bangert and with recent infrared absorption experiments. The width of the spectra can be explained qualitatively using the nonparabolic k_| dispersion of the individual subbands.     

Inelastic light scattering by collective excitations in the fractional quantum Hall regime

We report an inelastic light scattering study of long wavelength collective gap excitations of fractional quantum Hall (FQH) states at ν=p/(2p+1) for . The ν-dependence of the gap energy suggests a collapse of the collective excitation gap near . In a range of filling factors close to , where the FQH gap is believed to collapse, we observe a collective excitation mode that exists only at temperatures below 150 mK.     

Inelastic light scattering by acoustic phonons in quantum dots and quantum films

The Raman scattering spectra were analyzed in order to find and explain similarities and differences in the interaction between electrons and acoustic phonons in quantum dots and quantum films.     

Inelastic electron-photon scattering

It is suggested that colliding e⁺e⁻ beam machines may be used to study inelastic electron-photon scattering.     

Inelastic light scattering and X-ray diffraction from thick free-standing porous silicon films

The results of Raman scattering and X-ray diffraction studies of thick, free-standing, porous Si layers with thickness up to 500 μm are presented. The Raman scattering spectra have a distinctive difference from previous data for porous Si films on Si substrate and for thin, free-standing, porous Si layers. The experimental data can be explained by a modified phonon confinement model that accounts for a comprehensive strained Si nanocrystal. The comprehensive strain is a tensile one, and the value of stress can be up to 3 GPa. This interpretation is supported by data of X-ray diffraction measurements.     

Inelastic electron scattering in nickel

Using a 200 keV electron spectrometer, with an energy resolution of ～0.25 eV and a momentum resolution of ～0.2 A^-1, we have measured the energy loss spectra for transmission of electrons through thin (～600 Å) Ni films. These results address the general question of the validity of momentum transfer estimates in electron loss scattering.Using low-energy electron backscattering, we have observed the dipole forbidden M₁ transition at 112 eV. For high-energy scattering, we have observed this transition only at high momentum transfer (q? 2 A^-1). These results indicates sizable contributions from high momentum transfer collisions in the low-energy experiments.     

Inelastic scattering of heavy ions from deformed light nuclei at near-barrier energies

Angular distributions have been measured at energies near the Coulomb barrier for the systems ¹⁸O + ²⁴Mg, ¹²C + ²⁸Si and ^{16, 18}O + ²⁸Si for elastic scattering and inelastic scattering to the first 2⁺ states in ¹⁸O, ²⁴Mg and ²⁸Si. Coupled-channel calculations were required in order to reproduce the details of the strong Coulomb-nuclear interference minima. However, a satisfactory account of the main features of the data was obtained in a first-order DWBA analysis and with the closed formalism of Frahn. With the exception of ¹⁸O, it was sufficient to assume equal charge and optical-potential deformation lengths.     

Inelastic light scattering by a two-dimensional electron system with Rashba spin-orbit coupling

Inelastic light scattering by a two-dimensional system of electrons in a conduction band with Rashba spinorbit coupling is studied theoretically for the resonance case where the frequencies of the incident and scattered light are close to the effective distance between the conduction band and spin-split band in a III–V semiconductor. It is shown that, in contrast to the case of no spin-orbit coupling, the spectrum of the scattered light exhibits a plasmon peak even for strictly perpendicular polarizations of the incident and scattered light. There exists a configuration where the scattering spectrum exhibits features originating from single-particle transitions only. Furthermore, it is shown that, for the general case of elliptic polarizations of the incident and scattered light, the amplitude of the plasmon peak depends on the sign of the effective Rashba spinorbit coupling constant and the signs of the phases of the polarization vectors. This fact can be used to determine the sign of the Rashba constant.     

Inelastic diffractive scattering in nonperturbative QCD

We examine diffractive proton-proton scattering and photo- and electroproduction of mesons , where X denotes a proton or a final state, into which the proton can go by diffractive dissociation. Using a functional integral approach we derive the scattering amplitudes, which are governed by the expectation values of light-like Wegner-Wilson loops, which are then evaluated using the model of the stochastic vacuum. For the proton, we assume a quark-diquark structure. From the scattering amplitudes we calculate total and differential cross sections for high centre of mass energy and small momentum transfer and compare with experiments. Furthermore we calculate isovector form factors for the proton and the pion within the same model. Received: 30 January 2001 / Revised version: 29 June 2001 / Published online: 3 August 2001