CLASSICAL TRAJECTORY SIMULATION OF THE CLUSTER-ATOM ASSOCIATION REACTION I-AR-N-]I-2+NAR.1. CAPTURE OF IODINE BY THE I(AR)12 CLUSTER(I)

The atom-cluster association reaction I(Ar)n + I --> I2 + nAr (n = 12) is studied theoretically as a prototypical model of the effect of mic roscopic solvation on reaction dynamics. Classical trajectory methods are employed to model the dynamics. This paper focuses on the initial capture of I by the I(Ar)12 cluster. Two distinct minimum energy confi gurations for I(Ar)12 are considered: Ar6(I)Ar6, an icosahedron with I located at the center of the cluster; and IAr12, an icosahedron with I replacing one of the vertex Ar atoms. Both the structure and the tem perature dependence of the capture cross section are investigated. Cap ture rate constants at temperatures of 10 and 30 K are computed. Captu re cross sections for Ar6 (I) Ar6 + 1 predicted by a Langevin model ag ree well with those computed by classical trajectory simulation, revea ling that the capture process under investigation is determined by the long range interaction potential. In comparison with its gas phase co unterpart I + I, Ar6(I)Ar6 + I has a much larger capture cross section . One of the most important roles played by the microscopic solvation of chemical reactants in clusters is this enhancement of the cross sec tion for the initial capture process.