Quantum theory of the spectral density of the hydrogen bond in solution Part 2. A study of dimeric hydrogen-bond systems by perturbative method

Abstract

A methodological approach is proposed for the spectral density in solution of symmetric dimers involving hydrogen-bonded species for which Witkowski has shown that the full effective hamiltonian of the slow modes involves hamiltonians of driven oscillators perturbed by the parity operator. The driven damped quantum harmonic oscillator perturbed by the parity operator and embedded in a solvent is studied in the framework of the time-dependent perturbation theory involving the time evolution operator. Advantage is taken of the closed approach we have obtained (B. Boulil, J.-L. Dejardin, N. El Ghandour and O. Henri-Rousseau, J. Mol. Struct. (Theochem), 314 (1994) 83) for the autocorrelation function of a simple hydrogen bond. This allows us to extract a zeroth-order time evolution operator, which is then used in the interaction picture to obtain by perturbative expansion the autocorrelation function of the dimer.