Journal of Chemical Physics, Vol.109, No.13, 5221-5230, 1998
Resonance emission spectroscopy of predissociating SO2 (C)over-tilde(1 B-1(2)): Coupling with a repulsive (1)A(1) state near 200 nm
This work investigates the predissociative (C) over tilde(1 B-1(2)) state of SO2 by cooling the SO2 in a pulsed molecular beam and dispersing the emission upon resonant excitation into several different vibronic absorption features in the (C) over tilde state between 197 and 212 nm. Unlike at the lower excitation energies, the dispersed emission spectra at the higher excitation energies are dominated by progressions with odd quanta in the antisymmetric stretch mode nu(3) and combination bands with up to six quanta in the bending mode nu(2). The formidable intensity for emission into vibrational states with odd quanta in the antisymmetric stretch of the jet-cooled molecule suggests that the intermediate state at high energies in the excited state is of mixed electronic character at nonsymmetric geometries, so the operative components of the transition moment for excitation and emission may be different. We discuss our results by considering the avoided crossing seam and coupling between the (C) over tilde(1 B-1(2)) state and two dissociative states potentially involved in the electronic predissociation, the 3 (1)A(1) and the 1 (3)A(1) states.