Resonance Raman Intensity Analysis of Directly Photodissociating Haloalkane and Dihaloalkane Molecules

Abstract

We show some applications of resonance Raman intensity analysis to examine direct photodissociation reactions in polyatomic haloalkane molecules. These investigations indicate that direct C–I bond cleavage in iodoalkane and haloalkane molecules have distinctly multidimensional reaction coordinates that depend on the structure of the parent molecule. The Franck–Condon region photodissociation dynamics of the molecules studied seem to be qualitatively consistent with an impulsive ‘semi-rigid’ radical description of the photodissociation dynamics. The initial photodissociation dynamics also show intriguing correlation with the energy partitioning of the photoproducts as measured by time-of-flight transitional spectroscopy experiments. Gas and solution phase resonance Raman spectra and associated short-time photodissociation dynamics are usually very similar to one another except in cases where significant solvent symmetry breaking takes place (as in diiodomethane). Bond selective electronic excitation was investigated in several different dihaloalkane molecules and their short-time photodissociation dynamics exhibit some correlation with the amount of interaction between the two carbon-halogen chromophores. We discuss the ramifications of the initial photodissociation dynamics for energy partitioning and bond selective photochemistry.