Trajectory studies of atomic recombination reactions. IV. Recombination of iodine atoms

Abstract

The recombination of iodine atoms has been studied, between 300 and 1500°K, using classical 3D trajectory calculations and the Monte Carlo method of sampling. This approach, previously applied by A. G. Clarke and G. Burns [J. Chem. Phys. 56, 4636 (1972)] to bromine atom recombination, is presently extended to include the quasibound recombining atom-inert gas complexes. It. was found that such complexes provided an important recombination path. On the other hand, collisional complexes involving energy and angular momenta higher than those of quasidimers, rarely lead to recombination reactions. If the well depths for the IM interaction ε∞IM's are taken to be 0.7, 0.6, and 0.5 kcal/mole for M=Xe, Ar, and He, respectively, the trajectory calculations yield recombination rate constants in fair agreement with experiment. These well depths are 1.6, 1.9, and 5.3 times larger than the well depths between M and Xe, which is iodine's nearest neighbor in the periodic table. In the case of helium, the rate constants obtained by trajectory calculations are relatively insensitive to the variations in ε∞He value, which is thus less reliable than ε∞IXe and ε∞IAr. The redissociation of the nascent products was found to be substantial, ranging from 20% to 60%. The extent of redissociation was greater for lighter third bodies and at higher temperatures. Mass effect and pressure dependence in recombination reactions were also studied.