The Ionization And Dissociation Of The Small Gas Molecules Under Intense Femtosecond Laser Excitation

The ionization and dissociation of polyatomic molecules in femtosecond laserfield were studied in the article. The ions produced were detected by the TOF-MS.We investigated the behaviors of ionization and dissociation of CH₂I₂, CH₂IClmolecules with 60fs laser pulses at 800nm, 400nm in intense laser intensity rangeof 10¹³-10¹⁴Wcm^-2. We obtained the dependence of the yields of single andmulticharged ions on the laser intensity and the laser wavelength. We analyzed thedata and concluded: the field-induced ionization of the parent molecules tookplace first followed by ionization/dissociation which produced multichargedparent molecules and other fragments. The multicharged ions came from theCoulomb explosion of the multicharged parent ions. All the bonds broke upsimultaneously. We made a further study of the dependence of the kinetic energyreleases from the Coulomb explosion on the laser intensity. And then theinternuclear instances were calculated. In addition we also observed the moleculesions of I2, ICl which implied the concerted elimination happened in femtosecondlaser pulse. The observed phenomena were attributed to the interaction of theintense laser field with the molecular potential energy surfaces.