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Pb 2+ and Bi 3+ impurity centres in alkali‐earth oxides vibronic spectra, lattice dynamics, and electron‐phonon interaction
Author(s) -
Zavt G. S.,
Ellervee A. F.
Publication year - 1979
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220940249
Subject(s) - spectral line , phonon , atomic physics , hyperfine structure , chemistry , vibronic coupling , emission spectrum , electron , vibronic spectroscopy , lattice (music) , molecular electronic transition , physics , condensed matter physics , excited state , quantum mechanics , acoustics , astronomy
Abstract The vibrational structure in the emission spectra of Pb 2+ ‐ and Bi 3+ ‐doped CaO and SrO single crystal is studied at 4.2 K. The emission spectra are caused by the forbidden 3 A 1u → 1 A 1g transition which is initiated by the mixing of 3 A 1u and 3 T 1u states by T 1g lattice vibrations. A theory is given which takes into account, within the Cochran‐Cowley shell model, a linear vibronic coupling to A 1g modes and a change of force constants in the final electronic state. In most cases the main source of the electron‐phonon interaction is found to be the coupling of the transition with the electronic polarization of the nearest anions. The T 1g ‐symmetry‐projected phonon density of states is shown to be concentrated within a narrow interval of the order of 10 cm −1 . An estimate is presented showing that the hyperfine interaction can be responsible for the appearance of the weak zero‐phonon lines observed in the emission spectra.