SITE EFFECTS IN SPECTRA OF MATRIX-ISOLATED DIATOMIC-MOLECULES - A MODELING APPROACH

A model suitable for calculating electronic matrix shifts of diatomic molecules A-B in solid rare gases semi-quantitatively is presented. Guest-host interactions are modelled by summing over atom-pair potentials in a rare gas cluster of limited size embedded in a rigid crystal, and computing electrostatic interactions between the state-dependent dipole moment of the guest and the Rg atoms self-consistently. Numerical relaxation of the matrix yields state- and site-dependent solvation energies DELTA-V. The model is applied to NBr in solid argon, because (1) the dipole moments in the X 3-SIGMA-, a 1-DELTA, and b 1-SIGMA+ states are available from theory, and (2) spectroscopic constants have been determined for several trapping sites in argon (see subsequent paper). The model also yields approximate vibronic matrix shifts. These informations can be utilized to assign trapping sites of diatomic molecules.