State-selective photofragment imaging of iodine atoms via photodissociation of CF3I at 277 nm

Abstract

The photodissociation of CF3I cooled in a supersonic molecular beam has been investigated at 277 nm by state-selective photofragment imaging. Fragmented iodine atoms of two spin-orbit states are state-selectively ionized and projected onto a two-dimensional position-sensitive detector, to obtain their speed and angular distribution. The anisotropy parameter for an excited iodine atom I*(P-2(1/2)), beta(I*), is found to be 1.83 and is consistent with a dissociation lifetime in the order of 150-350 fs from rotational correlation function. Contrary to earlier reports, the parallel-like distribution for the ground state iodine atom I(P-2(3/2)) at this wavelength, shows a more favorable curve-crossing dissociation path (68%) from (3)Q(0) to (1)Q(1) and a less favorable direct dissociation path (32%) from (3)Q(1). The recoil energy distribution of I is found to be broader than that of I* and is correlated with a variety of energy disposal channels by an e symmetry vibration at the crossing point. The results are compared with previous works, and the strong photon energy dependence of the energy partitioning in CF3+I* channel and curve crossing are interpreted in terms of the final state interaction and curve crossing probability, respectively. (C) 1996 American institute of Physics.