Infrared spectra of medium strength H-bonds: beyond an adiabatic description of Fermi resonances

We extend a quantum non-adiabatic treatment of damped weak H-bonds involvin g Fermi resonances (D. Chamma, O. Henri-Rousseau, Chem. Phys. 248 (1999) 91 -104) in order to account for stronger H-bonds. For this purpose, we introd uce in the model the quadratic dependence of both the angular frequency and the equilibrium position of the X-(H) over right arrow ... Y stretching mo de on the intermonomer (X) over left arrow-H ...(Y) over right arrow motion s. We obtain the spectral density corresponding to this Hamiltonian by Four ier transform of the autocorrelation function of the dipole moment of the f ast stretching mode. This paper goes beyond a step toward a more comprehens ive theory of infrared bandshapes of H-bonded systems. Further development should lead to the release of a modeling software in this field. (C) 2000 E lsevier Science B.V. All rights reserved.