Excited Fragments from Excited Molecules: Energy Partitioning in the Photodissociation of Alkyl Iodides

摘要

Photofragment spectroscopy has been applied to the photodissociation of methyl, ethyl, n-propyl and iso-propyl iodide at 266.2 nm, both to study the process of unimolecular break-up of electronically excited molecules and to determine the energy distributions of the resulting excited fragments. By crossing a molecular beam with a powerful pulsed laser beam in high vacuum and monitoring the arrival times of the recoiling photofragments with a mass spectrometer detector, the translational energy distribution of the photodissociation products is measured. From energy balance, the distribution of fragment internal energy is then calculated. The experimental results are discussed in relation to the processes involved in alkyl iodide photodissociation lasers. Dynamic models for energy partitioning in molecular photodissociation are compared with the observed data. An illustrative example is given in modelling the bimolecular reactions of alkali metal atoms with alkyl iodides. (Author)