Above-threshold double ionization of He with attosecond soft X-ray pulses

In this study, we investigate two-photon double ionization of helium by attosecond intense soft X-ray pulse, based on numerical solution of the time-dependent Schrodinger equation (TDSE). We have constructed a simple model in which the ionization interval is chosen randomly, from which we calculate the energy of ejected electrons, taking account of the core relaxation time. The ionization of the second electron itself can proceed by photon absorption, without electron correlation. In this sense, the double ionization is not non-sequential.