Laser Phase Control of Electron-Nuclear Dynamics in Dissociative Ionization with Intense Femtosecond Pulses: Exact (non-Born-Oppenheimer) Numerical Simulations for H⁺₂

Exact numerical solutions of the time-dependent Schroedinger equation, TDSE of a 1-D H⁺₂ molecule are obtained for intense (I ≥ 10¹⁴ W/cm²) ultrashort (τ < 50 fs) laser pulses in order to examine laser control of the exact non-Born-Oppenheimer electron-nuclear dynamics in this simplest system. Such a non-perturbative treatment of the exact electron-nuclear dynamics allows us to examine the usefulness of simple two-colour (ω + 2 ω) coherent superpositions of laser pulses to control and manipulate electron and nuclear motion simultaneously. Three processes occur at these high intensities: molecular dissociation, electron ionization and Coulomb explosion. Varying the relative phase of the ω and 2 ω laser fields allows for the simplest control of the complete electron-nuclear dynamics of these three processes as shown by the present simulation. A major finding is that electron dynamics in the presence of intense ultrashort laser pulses is ´´counterintuitive´´, which can be explained in terms of a quasistatic tunnelling model. Control of the dissociative H+p channel can be explained in terms of ´´bond softening´´ occurring from laser-induced avoided crossings of dressed molecular potentials. Control of Coulomb explosion depends on a new nonperturbative phenomenon-Charge Resonance Enhanced Ionization, CREI, which occurs at large critical internuclear distances and can be explained in terms of ´´frontier´´ orbitals.