UV multiphoton ionization and IR photodissociation of CF3I cluster beams

摘要

This paper presents the results of studies into the ultraviolet multiphoton ionization (UV MPI) and infrared photodissociation of (CF3I)(n) clusters formed upon the ultrasonic outflow of CF3I molecules from a pulsed jet nozzle. The clusters were found to undergo UV MPI under the action of the XeCl-laser radiation (308 nm) to yield I+ and I+ ions as final products. The UV MPI yield was measured as a function of the radiation intensity and stagnation pressure. The efficiency of the UV MPI process was found to depend on the size of the clusters. The IR photodissociation of the (CF3I)(n) clusters was investigated as a function of the energy fluence and frequency of the CO2-laser radiation acting on the v, mode of the (CF3I)(n) molecule. The size of the clusters and their binding energy were estimated on the basis of the measurement results and model calculations. The main velocity characteristics of the (CF3I)(n) clusters in the beam, namely, the velocity of their directed motion and also the perpendicular and parallel velocity components of their thermal motion, were measured as a function of the (CF3I)(n) gas outflow conditions using their UV MPI and combined UV MPI + IR photodissociation. The thermal motion velocity distributions were demonstrated to be bimodal at the least. (c) 2007 Elsevier B.V. All rights reserved.