FEMTOSECOND LASER INTERACTIONS WITH METHYL IODIDE CLUSTERS. 2. COULOMB EXPLOSION AT 397 NM

Abstract As a continuing effort to elucidate the effects of the interaction of femtosecond laser radiation with clusters, we have extended our studies of Coulomb explosion to a determination of the role of laser wavelength on the process. In the present study, the interactions of methyl iodide clusters, formed in a supersonic expansion using argon and helium as carrier gases, were investigated at 397 nm using a Ti:sapphire femtosecond laser. These studies are a continuation of the work initiated on methyl iodide clusters using 795 nm ionization. The resulting atomic and cluster ions were analyzed in a reflectron time-of-flight (TOF) mass spectrometer. Based on a comparison of the current results and those presented for 795 nm ionization, several suggested mechanisms to account for the formation of highly charged species and their concomitant Coulomb explosion are examined. The resulting analysis indicates that the Coulomb explosion of methyl iodide clusters has characteristics of several of the proposed models to account for the phenomenon, but cannot be fully explained by any one of them.