Two-photon double ionization of lithium

The advent of free-electron laser technology has generated significant interest in the study of few-photon reactions at VUV and EUV wavelengths. Pioneering experimental measurements of recoil-ion momentum distributions for two-photon double ionization of lithium are currently underway at the Hamburg FLASH facility, augmenting previous measurements for helium and neon [1,2]. The time-dependent close-coupling (TDCC) method employed in this work is capable of treating single, double and triple photoionization of a three-electron system in full dimensionality [3]. However, the current work focuses on double ionization, and so a `frozen core' approach is used to treat the inner 1s electron. This work provides the first TDCC calculations to date of two-photon double ionization of lithium. This work also aims to extend the analysis of symmetrized amplitudes, previously invoked for double photoionization [4], to two-photon double ionization of a general two-electron atom. \\[4pt] [1] A. Rudenko {\em et al.}, 2008 {\emph{Phys.Rev.Lett.}} {\bf 101} 073003\\[0pt] [2] M. Kurka {\em et al.}, 2010 {\emph{New J. Phys.}} {\bf 12} 073035\\[0pt] [3] J. Colgan, M. S. Pindzola and F. Robicheaux, 2004 {\emph{Phys.Rev.Lett.}} {\bf 93} 053201\\[0pt] [4] A. S. Kheifets {\em et al.}, 2010 {\emph{Phys.Rev.A}} {\bf 82} 023403