Multiphoton ionization of aniline, aniline- 15N and aniline-2,3,4,5,6- d5: ionization and fragmentation mechanisms

Abstract

We report the resonant and non-resonant multiphoton ionization (MPI) spectra of aniline, aniline- 15N and aniline-2,3,4,5,6- d 5 obtained at wavelengths of 266,355 and 532 nm. Consideration of plots of fragment ion currents vs. laser pulse energy and analysis of the contributions from deuterated ions to total fragment ion intensities (obtained using aniline-2,3,4,5,6- d 5) have allowed characterization of the mechanisms involved in the overall ionization/fragmentation process at the three wavelengths. The resonant MPI at 266 nm is found to take place via initial molecular ion formation, followed by photofragmentation of this ion. In both the non-resonant cases the first step appears to be a rapid dissociation of the neutral molecule into smaller neutral entities. These are subsequently ionized, and photofragmentation of the ions produced then takes place. At 355 nm a minor contribution to the ionization/dissociation mechanism appears to involve molecular ion formation followed by photofragmentation.