Recollision Excitation in Quantum Descriptions of Double Ionization of Helium
Students C. Woolley, N. Harkema, E. Chen
Professor S. Haan
Tuesday, September 18, 3:45 p.m. SB110
When an atom with two or more electrons is exposed to a high-intensity laser pulse, the atom may doubly ionize. It is generally accepted that over a wide riange of laser intensities and frequencies the primary process for the double ionization involves 3 steps: (1) one electron ionizes; (2) the oscillating laser field pushes this electron away from the positive ion, then back; (3) the returning electron collides with the other electron and transfers energy to it. In the simplest case, the returning electron has absorbed enough energy from the laser field that both electrons can be free immediately after the collision. But what about situations in which the returning electron doesn't have that much energy? What if it doesn't even have enough energy to drive transitions from the ground state to the first excited state of the positive ion? We solve the Time Dependent Schrodinger Equation numerically for a simple one-dimensional model of helium to investigate recollision excitation, including what happens in the case of low energy recollisions.