The mechanisms of multiphoton ionization (MPI) and dissociation of CH3I have been studied using time-of-flight (TOF) mass spectrometer at 266 and 355 nm. MPI mass spectrum at 266 nm consists mostly of fragment ions. This is consistent with a neutral-fragment photoionization mechanism in which rapid one-photon dissociation occurs from the repulsive potential energy surface followed by MPI of neutral photofragments. The observation of parent ions at 355-nm excitation is indicative of parent-ionic ladder mechanism in which the parent ions are produced directly by two-photon excitation resonantly excited to Rydberg C state and then ionized through additional one-photon absorption to produce CH3I+. Fragment ions are produced by dissociation of CH3I+.
© 2007 Chinese Optics Letters
(020.4180) Atomic and molecular physics : Multiphoton processes
(020.5780) Atomic and molecular physics : Rydberg states
(260.5210) Physical optics : Photoionization
(260.7190) Physical optics : Ultraviolet
Li Li, Xianghe Kong, and Shudong Zhang, "Multiphoton ionization and dissociation of CH3I at 266 and 355 nm," Chin. Opt. Lett. 5, 315-317 (2007)