STATE-SELECTIVE PHOTOFRAGMENT IMAGING OF IODINE ATOMS VIA PHOTODISSOCIATION OF CF3I AT 277 NM

The photodissociation of CF3I cooled in a supersonic molecular beam ha s been investigated at 277 nm by state-selective photofragment imaging . Fragmented iodine atoms of two spin-orbit states are state-selective ly ionized and projected onto a two-dimensional position-sensitive det ector, 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 earli er reports, the parallel-like distribution for the ground state iodine atom I(P-2(3/2)) at this wavelength, shows a more favorable curve-cro ssing dissociation path (68%) from (3)Q(0) to (1)Q(1) and a less favor able direct dissociation path (32%) from (3)Q(1). The recoil energy di stribution of I is found to be broader than that of I and is correlat ed with a variety of energy disposal channels by an e symmetry vibrati on at the crossing point. The results are compared with previous works , and the strong photon energy dependence of the energy partitioning i n CF3+I channel and curve crossing are interpreted in terms of the fi nal state interaction and curve crossing probability, respectively. (C ) 1996 American institute of Physics.