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A Fermi resonance is the shifting of the energies and intensities of absorption bands in an infrared or Raman spectrum. It is a consequence of quantum mechanical mixing.〔Kazuo Nakamoto “Infrared and Raman Spectra of Inorganic and Coordination Compounds: Theory and Applications in Inorganic Chemistry (Volume A)” John Wiley, 1997. ISBN 0-471-16394-5〕 The phenomenon was explained by the Italian physicist Enrico Fermi. ==Selection rules and occurrence== Two conditions must be satisfied for the occurrence of Fermi Resonance: *the two vibrational states of a molecule transform according to the same irreducible representation of the molecular point group. In other words the two vibrations must have the same symmetries (Mulliken symbols). *The transitions (accidentally) have almost the same energy. Fermi resonance most often occurs between normal and overtone modes, if they are nearly coincident in energy. Fermi resonance leads to two effects. First, the high energy mode shifts to high energy and the low energy mode shifts to still lower energy. Second, the weaker mode gains intensity (becomes more allowed) and the more intense band decreases in intensity. The two transitions are describable as a linear combination of the parent modes. Fermi resonance does not really lead to additional bands in the spectrum. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fermi resonance」の詳細全文を読む スポンサード リンク
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