Chaos-induced breaking of the Franck-Condon approximation

We investigate the vibrational structure of electronic spectra for the transition from the non-degenerate $A$ state to $E$ states in $E_g\otimes e_g$ Jahn-Teller systems with the trigonal field included. In connection with the underlying chaotic behavior for vibronic energy levels in this model reported by the present authors in Phys.Rev.{\bf E68}(2003)046201, we extend the analysis by Longuet-Higgins et al. to the classically chaotic system. In particular, the triple-humped structure is manifest with increasing the anharmonicity. Such structure is completely inconsistent with the shape obtained from Franck-Condon(FC) approximation, and is caused by the chaos-induced beaking of the FC principle.