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

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 D₂rotational energy transfer forming the ortho(j = 2)-D₂+ I³⁵Cl(B,v = 1,j) products.