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.