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Theory of Fermi resonances in Raman and infrared spectra
Author(s) -
Monecke J.
Publication year - 1987
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250180705
Subject(s) - anharmonicity , fermi resonance , overtone , degenerate energy levels , perturbation (astronomy) , perturbation theory (quantum mechanics) , coupling constant , fermi gamma ray space telescope , physics , raman spectroscopy , quantum mechanics , eigenvalues and eigenvectors , spectral line , vibration , quantum electrodynamics
Fermi resonances are analysed in the literature either by degenerate first‐order perturbation theory or by the coupled oscillator model of Schwartz and Wang. Here the perturbation treatment is generalized, taking into account the coupling not only between a fundamental and an overtone, but also with other eigenstates, required by a proper treatment of the Bose character of vibrations. The resulting expressions for the frequency shifts differ from those of both other models. Numerical differences from the first‐order perturbation treatment are small in most cases. However, the results can be used to relate the empirical interaction constant of the coupled oscillator model to an actual anharmonicity constant.