Two-electron correlations in e+H-->e+e+p near threshold

Lattice calculations of the photoionization of Li

Calculations are presented for the double photoionization (with excitation) and triple photoionization of the Li atom. The motion of all three electrons is treated equally by solving the time-dependent Schrödinger equation in nine dimensions. A radial lattice is used to represent three of the nine dimensions, while a coupled channel expansion is used to represent the other six dimensions. Probabilities for photoionization are obtained by t--> infinity projection onto fully antisymmetric spatial and spin functions. Double photoionization cross sections for lithium leaving the ion in the 1s, 2s, and 2p states are presented. Good agreement is found with the measurements of Huang et al. [Phys. Rev. A 59, 3397 (1999)]] for the total double photoionization cross section and with the measurements of Wehlitz et al. [Phys. Rev. Lett. 81, 1813 (1998)]] for the triple photoionization cross section.

Time-dependent close-coupling calculations of dielectronic capture in He

We report on the first time-dependent close-coupling calculation of dielectronic capture into a doubly excited state of a two-electron atom. An incoming electron is represented by a Gaussian wave packet which collides with singly ionized helium in its ground state. The close-coupling equations describe the propagation of the total compound wave function on a two-dimensional radial lattice. By projecting this wave function onto a doubly excited state of neutral helium, we can determine the probability amplitude for dielectronic capture into one of these states and the subsequent autoionization from it.

Benchmark nonperturbative calculations for the electron-impact ionization of Li(2s) and Li(2p)

Three independent nonperturbative calculations are reported for the electron-impact ionization of both the ground and first excited states of the neutral lithium atom. The time-dependent close-coupling, the R matrix with pseudostates, and the converged close-coupling methods yield total integral cross sections that are in very good agreement with each other, while perturbative distorted-wave calculations yield cross sections that are substantially higher. These nonperturbative calculations provide a benchmark for the continued development of electron-atom experimental methods designed to measure both ground and excited state ionization.