Reaction dynamics of state-selected unimolecular reactants. Energy dependence of the rate coefficient for methyl isocyanide isomerization

Abstract

Intracavity c.w. dye laser techniques have been used to measure visible absorption spectra of gas-phase CH₃NC and CH₃CN and to photoactivate CH₃NC to reactive states with high selectivity. Photoisomerization kinetics of state-selected CH₃NC are reported and are used to determine optical absorption cross-sections and the energy dependence of the inherent unimolecular reaction rate coefficient k(ε), over an extended energy range(〈ε〉= 38–48 kcal mol^–1). The preparation, propagation and reaction of highly vibrationally excited CH₃NC are considered on the basis of all available spectroscopic and photochemical data. On the whole, there is only marginal evidence for nonstatistical behaviour in the state-selected CH₃NC reaction system.