15min:

P. Z. EL-KHOURY, A. N TARNOVSKY AND M. OLIVUCCI, Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403.

The photochemical reaction pathways following the promotion of CF₂I₂ and CH₂I₂ into their lowest lying electronically excited states are reported. The pathways are mapped using the complete active space self-consistent field (CASSCF) method. The S₀ to S₁ transitions in both molecules are found to be n to sigma* type transitions. The relaxation of the electronically excited CF₂I₂* and CH₂I₂* molecules from the initially excited Frank-Condon (FC) region to the product wells on the ground-state potential energy surface are found to occur via conical intersections. The results from our computational investigations explain the selectivity of photoproduct formation previously observed in gas-phase experiments on one hand, where some obvious conclusions about the condensed-phase photochemistry of these molecules can also be drawn.