Dissociative ionization and Coulomb explosion of CH in two-color asymmetric intense laser fields.

Directional fragment ejection from a tetrahedral molecule CH in linearly polarized two-color ( and 2) asymmetric intense laser fields (50 fs, 1.4 × 10 W cm, 800 nm and 400 nm) has been studied by three-dimensional ion coincidence momentum imaging. The H fragment produced from dissociative ionization, CH → H + CH + e, is preferentially ejected on the larger amplitude side of the laser electric fields. Comparison with theoretical predictions by weak-field asymptotic theory shows that the observed asymmetry can be understood by the orientation selective tunneling ionization from the triply degenerated highest occupied molecular orbital (1) of CH. A similar directional ejection of H was also observed for the low kinetic energy components of the two-body Coulomb explosion, CH → H + CH + 2e. On the other hand, the fragment ejection in the opposite direction were observed for the high energy component, as well as H produced from the Coulomb explosion CH → H + CH + 2e. Possible origins of the characteristic fragmentation are discussed.