State-to-state dissociation of SO 2 in C̃ 1B 2: Rotational distributions of the fragment SO

Abstract

The predissociation of SO 2 in the electronically excited C̃ 1B 2 state is studied in a state-to-state experiment. Using a frequency-doubled dye laser, the photodissociation of jet-cooled SO 2 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 3P 2 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 SO 2 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 SO 2 onto the rotation of the fragment SO were not completely convincing.