Laser-induced processes during the Coulomb explosion of H2 in a Ti-sapphire laser pulse

Theoretical simulations of processes leading to the complete Coulomb explosion of H-2 under a 150-fs, 800-nm Ti:sapphire laser pulse are made using two approaches. The first approach consists of purely nuclear, multichannel wave-packet calculations while the second approach involves electronic-nuclear, three-body wave-packet propagations on one-dimensional Coulomb-type potentials. The calculations that give proton kinetic energy spectra in qualitative agreement with the experimental results show that the high-energy, broadband found in these spectra results from the Coulomb explosion of H-2(+) following the enhanced ionization of the ion at a large internuclear separation, while the structures found at lower energies arise from the laser-induced dissociation of the molecular ion through the Floquet one- and two-photon pathways by the bond-softening mechanism. The experimental observations pertaining to the dependence of these structures on the field intensity indicate that the onset of:the molecular dissociation of H-2(+) occur at mid-pulse, i.e., at the end of the rise time of the laser pulse. The reported simulations illustrate the importance of coherently describing the initial phase of the dynamics, more precisely, the preparation of H-2(+) by the laser-induced first ionization of H-2. [S1050-2947(98)05411-0].