Hydrogen bonding 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]. 

Note that Marechal [48,75] proposed an original peeling-off procedure, but in a very different perspective, whose purpose is to eliminate from a given experimental spectrum the features brought by multiple Fermi resonances, thus revealing the intrinsic informations on the hydrogen bond dynamics. 

Figure 12. Hydrogen bond involving a Fermi resonance damping parameters switching the intensities. The lineshapes were computed within the adiabatic and exchange approximations. Intensities balancing between two sub-bands are observed when modifying the damping parameters (a) with y0 =0.1, and y5 = 0.8 (b) with ya = ys = 0.8 (c) with yB — 0.8 and ys — 0.1. Common parameters oto = 1, A = 150cm, 2g)5 = 2850cm-1, and T = 30 K.

Figure 13. Hydrogen bond involving a Fermi resonance relative influence of the damping parameters. Spectral densities 7sf(co) computed from Eq. (81). Common parameters a0 = 1, A = 160cm-1, co0 = 3000cm-1, co00 = 150cm-1, 2t05 = 2790cm-1, and T = 300K.

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