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Infrared Absorption by Localized Vibrations of H − and D − Ions in NaF and LiF Crystals
Author(s) -
Dötsch H.
Publication year - 1969
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.19690310226
Subject(s) - anharmonicity , phonon , ion , scattering , atomic physics , chemistry , absorption (acoustics) , dipole , infrared spectroscopy , infrared , absorption band , molecular physics , analytical chemistry (journal) , condensed matter physics , optics , physics , organic chemistry , chromatography
The infrared absorption due to localized vibrations of H − and D − ions in NaF and LiF is measured between 20 and 300 °K. The oscillator strengths are temperature independent. Measurements with uniaxial pressure show that the frequency of the local mode in NaF:H − is shifted by lattice distortions of the symmetry of Γ 1 +and Γ 3 +but not of Γ 5 + . In NaF:D − , LiF:H − , and LiF:D − two‐phonon decays are allowed resulting in relatively large halfwidths at low temperatures. In NaF:H − a two‐phonon decay is not possible and the halfwidth becomes smaller than the minimum spectral slit width of the grating spectrometer. The temperature dependence can be described by a scattering process in NaF:H − and by a composition of a scattering process with a two‐phonon decay process in the other systems. The anharmonic frequency shift is calculated to a first approximation. In a simple density approximation the side band spectra can be described better by anharmonicity than by nonlinear dipole moments.