Theory of Jahn-Teller Induced Optical Transitions

A new mechanism which makes a forbidden transition allowed by the Jahn-Teller interaction. Firstly the line shape of this Jahn-Teller induced transition at high temperature is calculated by using the Franck-Condon approximation. The main results are: In “Case A” of the singlet ground state and the nearly degenerate excited state the Jahn-Teller induced transition appears as a broad band while in “Case B” in which both the ground and excited states are nearly degenerate, it appears as a very sharp peak. Secondly its intensity and peak position at low temperature are calculated quantum mechanically. In the static limit of the Jahn-Teller interaction, the transition is too weak to be observed in Case A while it appears as a single absorption line in Case B. In the dynamical regime, the Jahn-Teller induced transitions disappear because of the motional narrowing.