One-atom cage effect in collinear I-2(B)-Ar complexes: A time-dependent wave packet study

Two-dimensional time-dependent wave packet calculations are carried out on a collinear model of the I-2(B)-Ar complex to investigate the possible kinematic origin of the one-atom cage effect in small van der Waals molecules. Three different excitation wavelengths are considered (496.5, 488, and 476.5 nm), and the dynamics are assumed to be restricted to the I-2 B state electronic surface, with no nonadiabatic transitions following the pump excitation. Good agreement with experiment is obtained. To investigate the sensitivity of observable final state distributions on the weak intermolecular potential between I-2 and Ar, three slightly different B state I-Ar interactions are employed for the case of 488 nm excitation. It is found that relatively small changes in the form and magnitude pf the weak van der Waals interactions can have a large effect on the final state distributions. These results suggest that the experimental data on I2Ar photodissociation-recombination can be explained by a purely kinematic one-atom cage effect on the B state electronic surface for a collinear population of I-2-Ar clusters, without the need to introduce nonadiabatic electronic effects. (C) 1996 American Institute of Physics.