THE INFLUENCE OF PARENT BENDING MOTION ON BRANCHING AT A CONICAL INTERSECTION IN THE PHOTODISSOCIATION OF CH3I, CD3I, CF3I

This work measures the change in branching between the CF3 + I(2P3/2) and I(2P1/2) product channels when one photodissociates vibrationally excited rather than cold CF3I at 248.5 nm. The experiment tests a model for the dependence of branching at a conical intersection on the amplitude of the dissociative wave function at bent geometries, a model which we propose here to explain previously observed differences in branching between the I(2P1/2) and I(2P3/2) channels at 248 nm for CH3I versus CD3I. In the CF3I experiment, we observe an increase in the branching from 13% to 17% I(2P3/2) products when the temperature of the CF3I parent is increased from 100 to 400-degrees-C, in agreement with the qualitative prediction of the model. We analyze the angular distributions of the photofragments to eliminate the possibility that the change in branching is due to an increased contribution from direct absorption to the electronic state correlating with I(2P3/2) products.