DC slice Imaging of CH3Cl photolysis at 193.3 nm

The DC slice imaging method is used to record energy- and angle-resolved distributions for both ground-state Cl (P-2(3/2)) and spin-orbit excited Cl* (P-2(1/2)) photofragments produced from the (A) over tilde -band photolysis of CH3Cl at 193.3 nm. The dissociation is found to be highly impulsive, with similar to90% of the available energy being released into translation. The angular distributions are predominantly perpendicular in the case of both the ground state and spin-orbit excited chlorine atom fragments, as characterized by recoil-energy averaged values of beta = -0.46 and beta* = -0.74 respectively, although we find considerable variation in both channels as a function of CH3 internal energy. In contradiction with previous measurements, we conclude that the transition to the (1)Q(1) state dominates much of the (A) over tilde -band profile, and this has significant implications for the description of the dissociation dynamics. Our findings are rationalized in terms of similar measurements performed with other methyl halides and their H atom substituted analogues.