Solution of a Vibronic Model for the Relaxed Excited State of theFCenter

Abstract

An exact solution is given for the vibronic problem posed by nondegenerate $s$ and $p$ electronic states interacting in cubic symmetry via a triply degenerate $T_{1\mathrm{u}}$ vibrational mode. In the strong-coupling limit the vibronic ground state is found to be $s$-like, irrespective of the order of the $s$ and $p$ electronic states in the unrelaxed configuration. Applications to the interpretation of Stark effects and other experiments on $F$ centers in alkali halides are discussed.