State-to-state dissociation of SO2 in C̃ 1B2: Rotational distributions of the fragment SO Original Research Article

The predissociation of SO2 in the electronically excited C̃ 1B2 state is studied in a state-to-state experiment. Using a frequency-doubled dye laser, the photodissociation of jet-cooled SO2 via single rovibrational levels is possible. A second tunable UV source is applied to detect the population of the molecular fragment SO by means of (1+1) REMPI–TOF technique. The observed rotational population distributions of SO(X 3Σ−, v″=1, 2) for dissociation closely above the respective thresholds are in good agreement with simulations from phase-space theory (PST). With increasing excess energy, deviations between experiment and PST model become significant: The spin component 3P2 of the fragment O is highly populated compared to the other two components of 3P, we observe population differences of the three spin components of SO in its ground state 3Σ. For small angular momenta (J<5) of the dissociating state of SO2 the rotational distributions of SO are distinctively structured. But they approach with increasing J the distributions according to the PST model. Simulations of such structures with a Franck–Condon mapping of the bending vibration of SO2 onto the rotation of the fragment SO were not completely convincing.