Multiphoton Processes in a Two-Electron Atom Using a Cray T3D

Abstract

Many-electron atoms interacting with intense coherent radiation presents many new challenges for the theorist. Theory was stimulated enormously in recent years by the discovery of high harmonic generation in closed-shell atoms^1,2, the discovery of above-threshold ionization³, and the demonstration of double and multiple-electron ionization in intense fields⁴. An ab initio theoretical description of such processes is greatly hampered by the non-perturbative nature of the Schrödinger equation in the intense field limit where the effects are most prominent, as well as by the extreme difficulty of the quantum mechanical few-body problem. Nevertheless, especially as laser pulses get ever shorter, there is an overwhelming to directly integrate the full time-dependent Schrödinger equation (TDSE) for the laser-driven atom. The direct numerical integration of the TDSE for a laser-driven one-electron atom (which in linearly polarized light reduces to a PDE in two spatial-dimensions and the time), is straightforward on modern workstations. By contrast, the TDSE for two-electron atoms in linearly polarized light involves five spatial-dimensions. Until recently this was beyond the power of supercomputers to solve without severe approximation.