Velocity map imaging of the photodissociation of CF3I: Vibrational energy dependence of the recoil anisotropy

The photodissociation of jet-cooled CF3I into CF3+I(2P3/2) and CF3+I*(2P1/2) has been investigated between 304 and 277 nm by using velocity map ion imaging. The two-dimensional images provide detailed information on the partition of available energy into kinetic and internal energy of the photofragments. Vibrational structure with spacing of 695±100 cm−1 is resolved in both I and I* images, indicating excitation of the umbrella mode ν2 of the CF3 photofragment. The fragment recoil anisotropies β(I) and β(I*) are determined as a function of the excitation wavelength and their variations are interpreted in terms of the crossing between the Q03 and Q11 dissociative electronic states. The high-resolution images allow the determination of the variation of the anisotropy parameter β as a function of the vibrational level of CF3 fragment, and provide a complementary method for the determination of the C–I bond energy. The vibrational dependence of the anisotropy values is discussed in terms of final-state interactions between the CF3 umbrella motion and the C–I dissociation coordinate, as discussed previously by Hennig et al. [J. Chem. Phys. 84, 544 (1986)].