A 4D wave packet study of the CH_3I photodissociation in the A band. Comparison with femtosecond velocity map imaging experiments

Abstract

The photodissociation of methyl iodide in the A band (λ=267 nm) has been studied both experimentally and theoretically [1]. Femtosecond pump-probe experiments in combination with velocity map imaging were carried out to measure the relative reaction times (clocking) of the different photodissociation channels. Multisurface nonadiabatic wave packet calculations in 3D were also previously performed using the best ab initio potential surfaces, nonadiabatic coupling, and transition dipole moments currently available [2-4]. Good general agreement was found between experiment and theory except for the channels involving excitation of the umbrella mode of the CH3 fragment [1]. New, more accurate absolute reaction times have been recently measured for the different dissociation channels, and improved multisurface wave packet calculations including 4 degrees of freedom have been recently carried out. Both the new experiments and simulations are reported in the present work.