Vibrational propensity in the predissociation rate of SO2(C̃ 1B2) by two types of nodal patterns in vibrational wavefunctions

The absorption and laser-induced fluorescence spectra of the C̃ 1B2–X̃ 1A1 band of SO2 were simultaneously measured between 221.5 and 208 nm under jet-cooled conditions. The fluorescence quantum yields above the dissociation threshold showed irregularity, reflecting a level specificity in the predissociation rate. The vibronic-level dependence in the predissociation rate was interpreted in terms of the nodal structure of the vibrational wavefunctions, constructed from a least-squares analysis of the observed vibrational energies in the C̃ state. The vibrational wavefunctions can be categorized into two types of localized wavefunctions: one stretching along the dissociation coordinate which tends to afford a much faster dissociation rate than the other which folds perpendicularly to the dissociation coordinate.