QUANTUM-THEORY OF THE SPECTRAL DENSITY OF THE HYDROGEN-BOND IN SOLUTION .2. A STUDY OF DIMERIC HYDROGEN-BOND SYSTEMS BY PERTURBATIVE METHOD

A methodological approach is proposed for the spectral density in solu tion of symmetric dimers involving hydrogen-bonded species for which W itkowski has shown that the full effective hamiltonian of the slow mod es 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 framew ork of the time-dependent perturbation theory involving the time evolu tion operator. Advantage is taken of the closed approach we have obtai ned (B. Boulil, J.-L. Dejardin, N. El Ghandour and O. Henri-Rousseau, J. Mol. Struct. (Theochem), 314 (1994) 83) for the autocorrelation fun ction of a simple hydrogen bond. This allows us to extract a zeroth-or der time evolution operator, which is then used in the interaction pic ture to obtain by perturbative expansion the autocorrelation function of the dimer.