The problem of an electron confined to a purely two-dimensional surface of a polar semiconductor interacting with the surface optical phonons and a surface Coulomb impurity is investigated in the framework of the Feynman-Haken path-integral formalism. The ground-state energy is obtained in the weakand strong-coupling limits by using the harmonic-oscillator and the hydrogenic effective potentials. A new dimensional scaling relation is proposed which holds only in the case of the harmonic-oscillator effective potential, and which, in the limit of vanishing impurity binding, reduces to the free-polaron scaling relation.
An approach has been developed to study the excitation of a ground-state H atom to the n =2 level under the simultaneous action of fast-electron impact and a monochromatic, linearly polarized, homogeneous laser beam. The laser frequency is assumed to be low (soft-photon limit) so that a stationarystate perturbation theory can be applied as is done in the adiabatic theory. An elegant method has been developed in the present work to construct the dressed excited-state wave functions of the H atom using first-order perturbation theory in the parabolic coordinate representation. By virtue of this method, the problem arising due to the degeneracy of the excited states of the H atom has been successfully overcome. The main advantage of the present approach is that the dressed wave function has been obtained in terms of a finite number of Laguerre polynomials instead of an infinite summation occurring in the usual perturbative treatment. The amplitude for direct excitation (without exchange) has been obtained in closed form. Numerical results for differential cross sections are presented for individual excitations to different Stark manifolds as well as for excitations to the n =2 level at high energies (100 and 200 eV) and for field directions both parallel and perpendicular to the incident electron momentum. Extension to a higher order of perturbation is also possible in the present approach for the construction of the dressed states, and the electron-exchange effect can also be taken into account without any further approximation.
In the present paper a method is developed for the determination of the orders of kinetics and activation energies of thermoluminescence (TL) glow curves recorded in a hyperbolic heating scheme. The suitability of the present method is tested by applying it both to numerically computed and experimental TL peaks. PACS No.: 78.60kn
The problem of an extrinsic surface optical polaron, bound to an impurity atom, near the surface is investigated for the first time in the framework o f a recently developed canonical transformation method. Energy and wave function for all ranges of the coupling constant (a) and the impurity parameter (/3) are obtained numerically following the canonical transformation method. For a strong impurity the relatively unimportant effect due to the image potential is neglected. The dependence of the energy, the wave function, and the induced potential on a, #? are obtained and shown graphically.Das Problem eines an ein Fremdatom gebundenen optischen Oberfllichen-Storstellenpolarons in der NLhe der Oberflliche wird zum ersten Ma1 im Rahmen der kiirzlich entwickelten Methode der kanonischen Transformation untersucht. Energie und Wellenfunktion werden in allen Bereiohen der Kopplungskonstanten a und des Storstellenparameters /3 numerisch erhalten. Fiir eine starke Storstelle wird der relativ unwesentliche Effekt des Bildpotentials vernachlllssigt. Die Abhlngigkeiten der Energie, der Wellenfunktion und des induzierten Potentials yon a und B werden berechnet und graphisch dargestellt.
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