A Simultaneous Photofragment Spectroscopy Measurement of Rovibronic and Translational Excitation in the CH3l A–Band Photodissociation System

The methyl iodide A-band photodissociation is investigated using a photofragmenttime-of-flight technique coupled with state specific detection of either the iodine atom ormethyl radical dissociation products by multiphoton ionization. The method is quitegeneral and allows the fragments' velocity and spatial distributions to be determinedsimultaneously with their rotational, vibrational and electronic excitation. It is shownthat methyl product from two competing dissociation channels, one direct, the othernecessitating an initial surface crossing, can be clearly distinguished by virtue of thecharacteristic translational excitation in each. The different rotational excitation whichis observed in these two channels is discussed in terms of the dissociation dynamics in themethyl iodide A-band continuum.