PICOSECOND MASS-SELECTIVE MEASUREMENTS OF MOLECULAR CLUSTER REACTIONS - (CH3I)N A STATE EXCITATION

The picosecond reaction dynamics of (CH3I)n clusters, initiated by à state excitation, were studied by molecular beam mass spectroscopy. Time-resolved measurements indicate that the prominent I2 and I2(CH3I)n-2 fragments are formed within the 10 ps limit of our resolution. The cluster dynamics and geometries allow for sequential loss of CH3 radicals and substantial caging of fragment I atoms and recombined I2 molecules. Loss of up to five CH3 radicals for cluster sizes n≥8 occurs within the 25 ps excitation pulse duration as indicated by the presence of ion signals such as I5(CH3I)3+. The evidence suggests that the extensive demethylation in the larger clusters is driven in part by the energy of intracluster recombination of two CH3 radicals and the elimination of ethane. © 1990.