THE BROWNIAN OSCILLATOR MODEL FOR SOLVATION EFFECTS IN SPONTANEOUS LIGHT-EMISSION AND THEIR RELATIONSHIP TO ELECTRON-TRANSFER

The Brownian oscillator model for the coupling of solvent motions to a solute's electronic transitions is applied to the calculation of absorption, relaxed fluorescence, and unrelaxed total emission (Raman and fluorescence) band shapes of a diatomic molecule in solution. The band shapes and the ratios of sharp scattering to broad fluorescence are explored as a function of the laser detuning from resonance, the parameters describing the solvent oscillator, and the excited-state lifetime, and direct comparisons with the stochastic theory, which does not contain the solvent-induced Stokes shift, are made. The relationship between the optical band shapes and the nuclear Franck-Condon factor for nonphotochemical electron transfer processes is also discussed within the Brownian oscillator model for the solvation coordinate. The limits of applicability of the ''high-temperature'' limit for the Brownian oscillator are established.