Hydrogen bonds, infrared Fermi resonances

Bratos and Hadzi have developed another origin of the anharmonicity of the fast mode X-H -Y, the Fermi resonance, which is supported by several experimental studies [1,3,63-70], Widely admitted for strong hydrogen bonds [67], the important perturbation brought to the infrared lineshape by Fermi resonances has also been pointed out in the case of weaker hydrogen bonds [53,71-73]. 

According to Colomban et al., within the broad band assigned to the hydrogen-bond mode there are several transmission windows, so-called Evans holes [355, 356], These holes are caused by the coupling of a narrow band with a very broad band. Principally, this is a phenomenon similar to the Fermi resonance. The interaction of two or more modes results in new modes and bands of different energies with corresponding transmission modes in the infrared spectrum and emissions in the Raman spectrum, which actually have been observed by Colomban et al. [350]. As a consequence, ex situ spectra have to be checked for unexpected transmissions. In the spectra recorded in situ and shown in Figure 25, band shifts as compared to band positions found in spectra... 

M. Song, H. Yamawaki, H. FujUiisa, M. Sakashita, K. Aoki, Infrared absorption study of Fermi resonance and hydrogen-bond symmetrization of ice up to 141 GPa. Phys. Rev. B 60(18), 12644 (1999)... 

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