Non-perturbative calculations of single and double ionization of He by swift U92+ projectiles

Abstract

We present non-perturbative calculations for single and double ionization of He atoms by 1 GeV amu−1 U92+ projectiles. We employ the time-dependent close-coupling method based on an expansion of a one-electron three dimensional wavefunction, for the single ionization, and an expansion of a two-electron six dimensional wavefunction, for the single and double ionization processes. The results are compared with experimental data and very good agreement is achieved. For this particular highly charged and swift projectile we include monopole, dipole, quadrupole, octopole and hexadecapoles for the projectile–atom interaction and we have made additional tests adding up superior multipole terms (triakontadipole and beyond). In order to obtain single differential cross sections for double ionization that are in very good agreement with experimental data, over 100 coupled channels are needed.