Electron-nuclear dynamics of H2+ in intense two-color laser fields : Asymmetries in electron ATI spectra

The time-dependent Schrodinger equation for the 1-D H 2 + molecule (with both nuclear and electronic degrees of freedom included) was solved numerically to study dissociative-ionization in the two-color (ω + 2ω) laser field. A wave function splitting technique was used, which allows one to circumvent the problem of lost information on electron flux due to absorbing boundary methods. This technique allows us to calculate the Above-Threshold Ionization (ATI) photo electron kinetic energy spectra in the presence of moving nuclei, as well as complete spectra of dissociating nuclear fragments, beyond the Born-Oppenheimer approximation. Strong directional, phase dependent, asymmetries in ATI electron spectra are observed. They are interpreted in the framework of the tunneling model. Classical trajectories of the electron (after tunneling) moving in the laser and ion field are calculated numerically, and it is demonstrated that this simple model explains well the asymmetries seen in our complete, quantum, three body simulations. The ATI spectra are considerably enhanced with respect to the H-atom spectra due to Charge-Resonance-Enhanced Ionization (CREI) in molecules.