Probing the Dependence of Long-Range, Four-Atom Interactions on Intermolecular Orientation. 4. The Dissociation Dynamics of H2/D2···ICl(B,v'=3) and the Observation of Efficient Vibrational-Rotational Energy Transfer.

Abstract

The vibrational predissociation dynamics of H2/D2···I35Cl(B,v'=3) complexes containing both para- and ortho-hydrogen prepared in different intermolecular vibrational levels were investigated. The Δv = -1 I35Cl(B,v = 2,j) rotational product-state distributions measured for excitation to the lowest-energy T-shaped levels of these complexes are mostly bimodal. The rotational distributions measured for excitation of the H2···I35Cl(B,v'=3) complexes are colder than those of the D2···I35Cl(B,v'=3) complexes, and there are only slight differences between those measured for the para- and ortho-hydrogen containing complexes. Excitation of the delocalized bending levels results in slightly colder rotational product-state distributions. The distributions suggest the dynamics result from more than impulsive dissociation off of the inner repulsive wall of the lower-energy H2/D2 + I35Cl(B,v = 2) potential surfaces of the products. The depths of these potentials and the energies available to these products also contribute to the dynamics. The formation of the Δv = -2, I35Cl(B,v = 1) product channel was only identified for excitation of levels within the ortho(j = 0)-D2 + I35Cl(B,v'=3) potential. The formation of this channel occurs via I35Cl(B,v'=3) vibrational to D2 rotational energy transfer forming the ortho(j = 2)-D2 + I35Cl(B,v = 1,j) products.