VIBRATIONAL RESONANCES IN MOLECULAR PHOTODISSOCIATION - FROM STATE-SPECIFIC TO STATISTICAL BEHAVIOR

We consider resonances in polyatomic molecules induced by coupled vibr ational motion on multidimensional potential energy surfaces. The quan tities of interest are the resonance positions, their widths as well a s the final-state distributions of the products. Depending on the well depth and the strength of the coupling between the internal modes, th e resonances can have properties ranging from state- and mode-selectiv e to statistical. For illustration we discuss three generic examples i n some detail: (a) the uv photodissociation of XNO molecules with X=F, Cl, CH3O etc; (b) the unimolecular dissociation of HCO in the ground electronic state and (c) the fragmentation of HO2 and NO2 also on thei r ground-state potential energy surfaces. In the first two cases, the results of nb initio theoretical calculations are related to recent ex perimental results.