Polarization dependent translational energy release observed in the photodissociation of C2F5I at 304.7 nm

Abstract

Using a state-selective photofragment translational spectroscopy, we determined the angular distribution and the polarization dependence of the velocity distribution for the iodine atom in the ground 2P3/2 and spin–orbit excited 2P1/2 states produced in the photodissociation of C2F5I at ∼304 nm. Consistent with theoretical and experimental results on other alkyl iodides, the excited state iodine is found to be produced predominantly from the parallel 3Q0←N absorption (βlab =1.63±0.06) with a high fraction of available energy released in translation (∼67%). The substantially lower anisotropy parameter (βlab =1.08±0.03) and the polarization dependent velocity distribution observed for the ground state iodine atoms, however, suggest that they are formed from two different excited states, by direct dissociation from the 3Q1 state (∼22%) and indirect dissociation via curve crossing from the 3Q0 to 1Q state (∼78%). The dissociation along the 3Q1 state is found to release about 3.1 kcal/mol more energy in translation than the dissociation via curve crossing from the 3Q0 state. This was blamed on the difference in the vibrational energy redistribution along the potential energy surfaces involved.