Convergent calculations of double ionization of helium: from ($\gamma$,2e) to (e,3e) processes

Abstract

The first absolute (e,3e) measurements, by Lahmam-Bennani et al [Phys. Rev. A {\bf 59}, 3548 (1999)], have been recently approximately reproduced by Berakdar [Phys. Rev. Lett. {\bf 85}, 4036 (2000)] and supported by Jones and Madison [Phys. Rev. Lett. {\bf 91}, 07321 (2003)], but with widely differing conclusions. The former indirectly implied that the Born-CCC-based calculations of Kheifets et al [J. Phys. B {\bf 32}, 5047 (1999) were invalid due to the reliance on the 1st Born approximation. The latter argued that the 1st Born approximation was valid, but the wrong initial state was used. We investigate these claims and find that the original calculations of Kheifets et al are reproduced whether the 2nd Born approximation is incorporated or if we use a ground state similar to that of Jones and Madison, but appropriately corrected as done by Le Sech and co-workers [J. Phys. B {\bf 23}, L739 (1990)].