TIME-DEPENDENT PHOTODISSOCIATION OF METHYL-IODIDE WITH 5 ACTIVE-MODES

Advances in the time propagation of multidimensional wave packets are exploited to present the A-band photodissociation dynamics of methyl i odide for five active vibrational modes on the three relevant excited ab initio potential surfaces. The five modes considered represent all of the experimentally observed dynamical activity. The only modes negl ected are the asymmetric C-H stretch and the asymmetric deformation of the methyl group. The kinetic energy operator corresponding to these five degrees of freedom is derived: The fully quantum mechanical calcu lation was implemented upon grids using 2880 distinct time-dependent c onfigurations, determined by the multiconfigurational time-dependent H artree algorithm, for each electronic state. All of the currently know n experimental results regarding the umbrella vibration, symmetric C-H stretching vibration, perpendicular rotation, and parallel rotation o f the photodissociated methyl radical fragment are well reproduced. Th e full wavelength dependence of all of these quantities is determined. The wavelength dependence of the energy deposited into translational, vibrational, and rotational motion is also given. The time evolution of the modes is presented in the context of correlated motion and its effect upon the dissociative process. Many of the details of the dynam ics inherent to the conically intersecting nature of the excited surfa ces is delineated. In particular it is shown that the Jahn-Teller dist ortion of the (1)Q(1) state is irrelevant in contributing to the perpe ndicular character of resonance Raman depolarization ratios. Results a re compared and contrasted to previous calculations employing the coll inear pseudotriatomic model with optimized empirical surfaces or the b ent pseudotriatomic model with the same ab initio surfaces.