摘要
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^＋.
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^＋.
