PHOTODISSOCIATION OF CF3I AT 248 NM - KINETIC-ENERGY DEPENDENCE OF THE RECOIL ANISOTROPY

The technique of polarized high-resolution photofragment translational spectroscopy has been applied to disentangle the dissociation processes occurring upon excitation of CF3I at 248 nm. To this end the anisotropy parameter-beta of the photofragment recoil was determined as a function of the fragment kinetic energy. For the reaction producing CF3 and spin-orbit excited iodine atoms I*(2P1/2) a positive anisotropy parameter with a maximum value-beta = +1.75 is observed. In the case of the reaction which yields CF3 and ground state iodine I(2P3/2) the beta-parameter is positive at high kinetic energy and drops sharply to negative values at lower kinetic energies. These results show that the photofragment signal arises from an initial excitation of two potential energy surfaces with different electronic angular momenta (the so-called 3Q0 and 1Q1 states). A partitioning of the photodissociation signal indicates that the 3Q0 state contributes 80% and the 1Q1 state 20% of the total absorption at 248 nm. Irrespective of the spin-orbit state of the I atoms, the average internal energy of the CF3 counterfragments is almost-equal-to 700 cm-1 larger for the 1Q1 component than for the 3Q0 component. This finding indicates that the dissociation dynamics near the Franck-Condon region has a significant influence on the energy disposal into the photofragments.