Single and double photoionization of Ne8+

Abstract

A direct solution of the time-dependent Dirac equation is used to calculate the single and double photoionization cross sections for Ne8 +. Expansion of a two-electron wavefunction in coupled spin–orbit eigenfunctions yields time-dependent close-coupled equations for quad-spinor radial wavefunctions. The repulsive interaction between electrons includes both Coulomb and Gaunt interactions. The fully-correlated ground state radial wavefunction is obtained by solving a time-independent inhomogeneous set of close-coupled equations instead of a relaxation of the time-dependent close-coupled equations in imaginary time. A Bessel function expansion is used to include both dipole and quadrupole effects in the radiation field interaction for both the ‘velocity’ and ‘length’ gauges. Propagation of the time-dependent close-coupled equations in real time yields single and double photoionization cross sections for Ne8 + at energies easily accessible at advanced free electron laser facilities.