Ionization and dissociation of CH3I in intense laser field

The ionization-dissociation of methyl iodide in intense laser field has been studied using a reflection time-of-flight mass spectrometry (RTOF-MS), at a laser intensity of CH3++I2+ is caused by Coulomb explosion. The valid charge distance R-c between I2+ and CH3+, at which enhanced ionization of methyl iodide occurs, is obtained to be 3.7 A by the measurements of the KERs of the fragments CH3+ and I2+. For the CH3In+ (n >= 3), the KERs of the fragment ions CH3p+ and Iq+ are attributed to the Coulomb repulsion between CH3p+ and Iq+ from R-c approximate to 3.7 A. The dissociation of the fragment CH3+ is also discussed. By the enhanced ionization mechanism and using the measured KER of Iq+, all the possible Coulomb explosion channels are identified. By comparing the abundance of fragment ions in mass spectrum, it is found that the asymmetric dissociation channels with more charges on iodine, q > p, are the dominant channels. (c) 2007 American Institute of Physics