Field-Assisted Dissociative And Ionization Of Dihalomethane Compounds Induced By Femtosecond Laser Field

The field-assisted dissociative ionization of dihalomethane compounds irradiated by 60 fs 800 nm laser with different laser intensities (1 4><1014 W/cm2) is studied both experimentally and theoretically in the article. In the experimental aspect, fragmentation patterns are observed with a time of flight mass spectrometer. The results indicate that the fragmentation and ionizations mechanisms of dihalomethane molecule in intense laser fields are heavily dependent on laser intensity. In the theoretical aspect, Gaussian03 program is applied to calculate the transition states and chemical reactions and the potential energies surface curves of two dihalomethane molecule. The calculation results shows potential energies of CH₂I₂⁺ and CH₂ICl⁺ as functions of the bond distances such as C-I and C-H bond etc. under external field with different intensities. Both theory and experiment can draw the conclusion. Firstly, field ionization mechanism is dominant; Secondly, field-assisted dissociation of parent ions leads to cracking of the chemical bond in a stepwise manner; Finally, all kinds of fragment ions are detected. The calculations explain well our experimental observations.