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On the Infra‐Red Absorption of Crystals Due to Lattice Vibrations
Author(s) -
Wehner R.
Publication year - 1966
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.19660150233
Subject(s) - anharmonicity , phonon , dipole , oscillator strength , lattice (music) , dispersion (optics) , condensed matter physics , quartic function , lattice vibration , dispersion relation , absorption (acoustics) , physics , chemistry , quantum mechanics , optics , mathematics , spectral line , acoustics , pure mathematics
The theory of the infra‐red absorption and dispersion of crystals due to lattice vibrations is reinvestigated. Dipole moments up to third order and cubic and quartic anharmonicity in the displacements of the nuclei are considered. Using Green functions and the functional method of Martin and Schwinger a dispersion formula is derived in terms of renormalized phonons. The introduction of a renormalized linear dipole moment causes the oscillator strength to become a complex function of frequency. In the case of diatomic ionic crystals the frequency shift and lifetime of the dispersion oscillator can be obtained from the measured optical parameters.