We discuss directional dependence in the time development of spatial wavefunctions, which includes jet formation, for two-electron model atoms exposed to intense laser fields. Two competing scenarios for double ionization are evident: (1) both electrons emerge simultaneously from the core region and on the same side of the nucleus, and (2) the electrons detach on opposite sides but not simultaneously. The importance of the electron-electron repulsion contribution to the competing processes is investigated for various laser intensities.
Haan, Stanley L.; Hoekema, N.; Poniatowski, S.; and Liu, W. C., "Directional correlation in direct and sequential double ionization of model atoms" (2000). University Faculty Publications. 486.