SOLVENT EFFECTS ON OPTICAL-EMISSION AND ABSORPTION-SPECTRA - THEORETICAL CALCULATION OF THE (1)(N, PI-ASTERISK) TRANSITION OF FORMALDEHYDE IN SOLUTION

A nonequilibrium polarizable continuum model, proposed in a previous p aper (J. Chem. Phys. 1993, 98, 7375), is applied to the study, at CIS and CISD levels, of solvent effects on the electronic structure of the (1)(n, pi) transition of formaldehyde. To obtain a proper descriptio n of the excited state properties in solution, the generalized density matrix must be employed. The effects of the electrostatic dielectric potential, dispersion, and the Stark term, as well as the specific sol ute-solvent interaction are analyzed. The contribution to the solvent shift from the dispersion component is of comparatively minor importan ce in the absorption process, but constitutes an appreciable fraction of the total shift in the emission process. The contribution of the St ark effect term is very small and may be neglected. Explicit addition of water molecules to the carbonyl compound is necessary to account fo r the observed blue shift.