Polarization control of direct (non-sequential) two-photon double ionization of He

An ab initio parametrization of the doubly-differential cross section (DDCS) for two-photon double ionization (TPDI) from an s(2) subshell of an atom in a S-1(0)-state is presented. Analysis of the elliptic dichroism (ED) effect in the DDCS for TPDI of He and its comparison with the same effect in the concurrent process of sequential double ionization shows their qualitative and quantitative differences, thus providing a means to control and to distinguish sequential and non-sequential processes by measuring the relative ED parameter.