Cluster-induced photochemistry of CH3I at 248 nm

Abstract

We have carried out a systematic study of the 248 nm excimer-laser photodissociation of small methyl iodide clusters in a free jet expansion. Ground electronic state I2 is formed from the photolysis of methyl iodide dimers and detected via the laser induced fluorescence (LIF) excitation spectrum of the (B–X) transition. The internal energy of the I2 is approximately 2.5 kJ/mol and is the same for CH3I seeded in CO2, Ar, Xe, O2, and He, as well as for the neat expansion and deuterated sample. A room temperature flow cell experiment shows that the reaction channel I*+CH3I→I2+CH3I does not contribute to the measured I2 signal. The results strongly imply that a cluster-induced cooperative effect is responsible for the I2-producing chemistry.