Dissociative ionization and Coulomb explosion of CH3I in intense femto second laser fields

Abstract

The interaction of CH3I molecules with 100 fs 800 nm linearly polarized laser fields has been investigated at the intensity region from 2.6 × 1014 to 5.8 × 1014 W/cm2 by means of a velocity map imaging method. The kinetic energy distribution of the various atomic fragment ions I q+ (q = 1–3) has been measured and reproduced by a fit of multiple Gaussian functions. Several dissociative ionization and Coulomb explosion channels were identified for I q+ (q = 1–3). As expected for a geometric alignment dominated interaction process the anisotropic angular recoil distributions of the atomic ion fragments are peaked in the laser polarization direction. The kinetic energy release (KER) of I q+ (q = 1–3) depending upon the laser intensity has been investigated. The relative weight of the various contributions from the identified dissociative ionization (DI) and Coulomb explosion (CE) channels is found to depend strongly on the laser intensity.