摘要:

AbstractThe dielectric function of Au films is determined ellipsometrically in the wave‐number ranges 700 cm−1≦v≦ 1900 cm−1and 2500 cm−1≦v≦ 3000 cm−1as well as for 8900 cm−1≦v≦ 32300 cm−1(1.1 eV ≦ ħω ≦ 4 eV). The spectra are discussed taking into account intra‐ and interband transitions. An energy‐dependent plasma frequency and damping is found. The sample effects are essentially described within an effective medium approximation assuming the influence of voids. Some peculiarities of the frequency dependence of the damping parameter are like

ISSN:0370-1972    

DOI:10.1002/pssb.2221370115

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe theory of impurity‐mediated free‐carrier absorption in n‐GaAs bulk material is extended to quasi‐two‐dimensional structures. The surfaces are treated within the classical infinite‐barrier model and the electron—electron interaction within the random‐phase approximation. Screening due to phonons is also considered. Using temperature‐dependent Green's functions and starting from the Kubo formula a general expression is derived for the free‐carrier absorption coefficient including both bulk and surface contributions. In thick n‐GaAs slabs coupled phonon—plasmon bulk excitations give rise to distinct peaks in the absorption spectrum. These structures are increasingly washed out with decreasing thickness. For comparison impurity‐mediated free‐carrier absorption spectra of non‐interacting electrons have also been calculated. At and below the bulk plasmon frequency the absorption is reduced due to screening. The absorption increases on the other hand wit

ISSN:0370-1972    

DOI:10.1002/pssb.2221370116

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe temperature dependence of the resonance splitting is calculated for pairs of translationally equivalent and inequivalent molecules in a molecular crystal using a canonical transformation method. The model Hamiltonian takes into account the excitonic transfer matrix element and linear local coupling between excitons and both acoustic and optical phonons. The calculations are successfully applied to optical data obtained for triplet excitons in phenazine.

ISSN:0370-1972    

DOI:10.1002/pssb.2221370117

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe thermodynamics of multicomponent plasmas is investigated using a theoretical description where the free energy as a function of density and temperature is the basic quantity. The correlation contribution to the free energy and the chemical potential as well as the excess pressure (exchange plus correlation) are calculated at arbitrary degeneracy by summation over the complex Matsubara frequencies. With increasing degeneracy the numerical effort may be reduced with the help of the large wave‐number approximation or plasmon—pole expressions for the dielectric function. The temperature dependent self‐energy is calculated in the same way. Numerical results are given for the electron system, a hydrogen plasma, and for the electron—hole plasma in highly excited semicon

ISSN:0370-1972    

DOI:10.1002/pssb.2221370118

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractA disordered excitonic system perturbed by the Gauss‐Markov noise approximating the exciton‐phonon interaction is investigated. The structure of the mass operator is discussed in dependence on the eigenfunctions of the excitonic Hamiltonian. Explicit calculations of the density of states and the imaginary part of the DF ϵ2(ω) are performed for Lorentzian static disorder. The influence of the breaking of thek‐selection rule or of fluctuations in the transition matrix elements on the frequency dependence of ϵ2(ω) is c

ISSN:0370-1972    

DOI:10.1002/pssb.2221370119

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractA theoretical study of the subband structure and impurity related levels in GaAs/Ga1−xAlxAs heterojunction is give

ISSN:0370-1972    

DOI:10.1002/pssb.2221370120

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractUsing a tight‐binding model for the transition‐metal perovskite‐type oxides ABO3a method of electronic Green function calculation is developed. In the framework of this technique the analytical equations for the local levels of atomic vacancies are obtained. The vacancy potential is calculated in the dielectric approximation including the ion displacements on the long ranges from the vacancy site and the electronic screening in the vicinity of the defect. It is shown that the appearance of the local levels in the forbidden gap is caused by the perturbation potential on the first neighbours of the vacancies. The energies of electronic excitations from the local levels are evaluated using the generalized transition state scheme. Donor levels close to the conduction band for the oxygen vacancy and acceptor levels for the A and B ion vacancy are obtained. The correlation between the results obtained and the physical properties of the perovskite oxides is disc

ISSN:0370-1972    

DOI:10.1002/pssb.2221370121

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractAbsorption energies of the F+‐centre in Li2O and other alkali‐oxides of antifluorite structure are calculated numerically using the point ion and model potentials incorporating core repulsion based on the modified Bartram, Stoneham and Gash pseudopotential as proposed by Matthew and Green. Other effects such as electronic polarization and ionic distortion are also considered. The results obtained are in good agreement with the experimentally assigned value for the band peak position and with the recent variational calculations by Ong on the same syst

ISSN:0370-1972    

DOI:10.1002/pssb.2221370122

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect is studied of spin—orbit interaction and low‐symmetry field on the absorption ratios of the wide bands of the excited‐state absorption spectrum and similar bands of the ground‐state absorption spectrum of d3‐configuration. The study includes calculations of the energy of the pure electron transitions and the analysis of the composition of the eigenfunctions of the Cr3+ions in ruby, magnesium oxide, and emerald in the cubic field approximation and taking mixing of all terms of the double trigonal group into account. The results are compared to the experimental values of the ratios of the oscillator strengths of the transitions compared. It is shown that the ratios depend strongly enough on the crystal field parameters and the parameter of the spin—orbit interaction. The influence of the interaction under consideration on the lasing parameters i

ISSN:0370-1972    

DOI:10.1002/pssb.2221370123

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractLow temperature (from 4.2 up to 30 K) photoluminescence spectra of InSe crystals containing macroscopic inclusions of neutral slightly soluble impurities (gadolinium, anthracene, fluorene etc.) are studied. The inclusions are of 0.1 to 0.5 μm in size. A substantial rise (by one or more orders in magnitude with respect to the initial spectrum of undoped crystals) of the exciton luminescence intensity is observed at relatively moderate doping doses (the impurity concentration less than 0.5 wt%) in the region of longitudinal exciton frequency ωL. To explain this effect a model is developed, which takes into account the scattering of lower branch polaritons at macroinclusions and their transformation into polaritons of the upper branch without changes in energy. The calculated temperature and frequency dependences of upper polariton branch luminescence are close to those measured experimentally despite of the practically non‐parametric way of the calculati

ISSN:0370-1972    

DOI:10.1002/pssb.2221370124

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY