Probing the Dependence of Long-Range, Four-Atom Interactions on Intermolecular Orientation. 4. The Dissociation Dynamics of H 2 /D 2 ···ICl(B, v '=3) and the Observation of Efficient Vibrational-Rotational Energy Transfer.

The vibrational predissociation dynamics of H 2 /D 2 ···I 35 Cl(B, v '=3) complexes containing both para - and ortho -hydrogen prepared in different intermolecular vibrational levels were investigated. The Δ v = -1 I 35 Cl(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 H 2 ···I 35 Cl(B, v '=3) complexes are colder than those of the D 2 ···I 35 Cl(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 H 2 /D 2 + I 35 Cl(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 Δ v = -2, I 35 Cl(B, v = 1) product channel was only identified for excitation of levels within the ortho ( j = 0)-D 2 + I 35 Cl(B, v '=3) potential. The formation of this channel occurs via I 35 Cl(B, v '=3) vibrational to D 2 rotational energy transfer forming the ortho ( j = 2)-D 2 + I 35 Cl(B, v = 1, j ) products.