Calculation of the vibronic structure of solute solvent van der Waals clusters

Abstract

Calculations of the eigenvectors and eigenvalues for the van der Waals clusters benzene (Ar)1, (CH4)1, (H2O)1, and (NH3)1, and s-tetrazine (Ar)1 are presented. The calculations are based on an atom-atom Lennard-Jones (6-12-1-10-12) potential function, which includes hydrogen bonding, and a normal coordinate analysis. The clusters are treated as giant molecules. The results of these calculations are then used to assign the van der Waals vibronic spectra of the above clusters. Agreement between calculations and experiments is excellent for binding energies, symmetries, and van der Waals frequencies. The S sub 2 to S sub 1 vibronic transistions of the above clusters are essentially completely assigned based on these calculations. A major conclusion of this work is that the low frequency van der Waals torsions and bends are active in Herzberg-Teller vibronic coupling. A number of approximate diatomic molecule calculations are compared to the above procedure and thereby evaluated.