Photofragment investigations of the 280 nm photodissociation of methyl iodide using rempii atom detection

Abstract

The A-band photodissociation of CH3I has been investigated around 280 nm, to the red of the absorption maximum. Iodine atom photofragments are state-selectively detected by multiphoton ionization and a re-examination of the pertinent region of the atomic iodine MPI spectrum is presented. From a time-of-flight photofragment analysis β anisotropy parameters are deduced for the I* and I dissociation channels. The reduction in β for the latter is discussed in terms of the surface crossing in this channel. ν2 umbrella mode methyl radical excitation distributions are also derived and compared to previous measurements at 248 and 266 nm, and to the predictions of a multisurface photodissociation model.