Far-infrared s→p ± interexciton transitions in InGaAs/GaAs coupled double quantum wells

We consider s→p ^± interexciton far-infrared (FIR) magnetooptical transitions in coupled double quantum wells (DQWs). Spatially direct (intrawell) and indirect (interwell) excitons in strained In_xGa_1−x As/GaAs symmetric DQWs with a simple valence band are considered. The evolution of the transition energies and oscillator strengths as functions of the transverse magnetic field B in different regimes is studied: we consider the direct regime (zero and low transverse electric field ℰ), the indirect regime (high ℰ), and the indirect-direct crossover (induced by increasing B at intermediate ℰ). Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 198–202 (10 August 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Photoluminescence of self-assembled GeSi/Si(001) nanoislands of different shapes

The dependence of the photoluminescence spectra of structures with self-assembled GeSi/Si(001) islands on Ge deposition temperature was studied. The position of the island photoluminescence peak maximum was found to shift nonmonotonically with decreasing Ge deposition temperature. The blue shift of the island photoluminescence peak with the growth temperature decreasing from 600 to 550°C is assigned to the change in the island shape occurring in this temperature interval accompanied by a strong decrease in the average island height.     

Conversion of acoustic bending vibration frequency in a freely suspended ferroelectric liquid-crystal film

A nonlinear acoustic effect was observed experimentally in a freely suspended ferroelectric liquid-crystal film. The effect consisted of a change in the frequency of the film bending vibrations under the action of a varying electric field. The up-and down-conversion efficiencies were found to be 50 and 30%, respectively.     

Violet-to-red photoluminescence of spiro-TAD organic films doped with different organic dyes

Photoluminescence (PL) and photoluminescence excitation (PLE) spectra of undoped spiro-TAD films and spiro-TAD films doped either by the organic dyes coumarin 7 or DCM as well as by both of these dyes simultaneously were investigated at different dye concentrations. A widened PL spectrum caused by doping was encountered and violet-to-red emission was obtained. It was established that excitation of the dyes is realized most efficiently through spiro-TAD. The overall integral PL intensity of the coumarin 7 doped films increased with dye concentration due to the suppression of nonradiative recombination in the film caused by a transfer of spiro-TAD excitation energy to the dye molecules. Mainly radiative energy transfer from semiconductor to dye molecules occurs in the case of DCM doping. No mutual influence on the luminescence of both dyes in the spiro-TAD film was observed and as a consequence, the PL band intensity of each dye can be adjusted separately.     

PMR spectra of difuroyl peroxides

The PMR spectra of difuroyl peroxides were recorded. It is shown that the introduction of a peroxide grouping in place of an anhydride grouping does not lead to changes in the spectrum.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, p. 163, February, 1974.