Spectroscopic spin-boson model in the adiabatic limit: Application to optical line shapes.

Abstract

A mapping of the spin-boson model to problems concerning nuclear dynamics on two nonradiatively coupled excited electronic potential surfaces is solved in the adiabatic or low oscillator frequency limit. Emphasis is placed on application of the theory to optical line shapes associated with electronic absorption and resonance Raman processes. The solution is in the form of a one-dimensional quadrature, even in the multimode case. The validity of the solution is checked by comparison to exact results obtainable in the single-mode problem. Then, two prototypical multimode coupling scenarios are investigated with the model. Finally, it is pointed out that a much more flexible class of solutions can be obtained by a straightforward extension of the theory developed here. In fact, the influence of an adiabatic bath on the spectroscopic dynamics of an arbitrary system can be included by computing the quantum dynamics of the system for a family of potentials and averaging this dynamics appropriately.