Knowledge Bank

The predissociation dynamics of several Rydberg states of methyl iodide are studied theoretically, pertinent to a recent femtosecond pump-probe $experiment1$. The theoretical model involves two active modes in the predissociation, i.e. the C-1 stretch and $C-H3$ stretch. The quantal molecular dynamics on two-dimensional model potential energy surfaces show that the initial dynamics involves non-adiabatic transitions from the Rydberg state to the dissociative state along a vibrational mode involving the light atoms. Subsequent dynamics on the dissociative state lead to the C-1 bond cleavage. The theoretical calculations reproduced not only the experimental decay transients, but also the large isotope effect and mode specificity in the predissociation rate. The two dimensional dynamics underscore the importance of multidimensionality in the predissociation dynamics of these Rydberg states.