The Absorption Spectrum of a Defect-Center Model.
ARMY MISSILE RESEARCH DEVELOPMENT AND ENGINEERING LAB REDSTONE ARSENAL AL PHY SICAL SCIENCES DIRECTORATE
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Calculations of the absorption spectrum were made for a system consisting of an electron moving in the Coulomb field of two point ions which vibrate harmonically with a fixed phase relation connecting their displacements. The electron-ion interaction was approximated by the first two terms in its Taylor expansion in the displacements of the ions from their equilibrium positions and computation was carried out in second-order perturbation theory by use of the hydrogen molecular ion wave functions of Bates, Ledsham, and Stewart. An expression for the spectral function in terms of the temperature-dependent double-time Greens functions for the electron-ion system formed the basis for determination of the positions and magnitudes of the absorption lines. The absorption spectrum was calculated for two different electronic transitions, for a set of ion vibrational frequencies and equilibrium separations covering the range of optical phonon frequencies and separations found in most lattices, and for a set of five relative phases of the motion of the two ions running from 0 to pi. It is expected that the results obtained give some qualitative indication concerning the behavior of a defect center interacting with a moderate- to high-frequency vibrational mode in a lattice. Author
- Solid State Physics