Dissociative ionization of H-2(+) in an intense laser field: Charge-resonance-enhanced ionization, Coulomb explosion, and harmonic generation at 600 nm

The time-dependent Schrodinger equation for H-2(+) in a 600-nm, intense (I greater than or equal to 10(14) W/cm(2)) laser field is solved numerically for a model which uses the exact three-body Hamiltonian with one-dimensional nuclear motion restricted to the direction of the laser electric field and three-dimensional electronic motion. High ionization rates of H-2(+) are found, exceeding those of neutral atomic hydrogen. This confirms, by the rigorous, full dynamical calculation, the recently discovered charge-resonance-enhanced ionization (CREI) - all previous demonstrations of CREI were based on the ''frozen nuclei'' model. The numerical kinetic-energy spectra of dissociating fragments are compared with recent experimental results. They can be interpreted by a simple bond softening mechanism (or laser-induced avoided crossing in a dressed state representation), in which the binding forces are completely suppressed by the strong electric field and thus the dissociating fragments move as free particles with a kinetic energy close to their initial vibrational energy until they reach a critical distance R=R(c) congruent to 8 bohr, where they are rapidly ionized, due to CREI. The harmonic generation spectra calculated from our non-Born-Oppenheimer simulations show that the high harmonics are also generated when the nuclei cross this critical distance R=R(c).