Accurate treatment of doubly-excited Rydberg resonance states and dc-field ionization rates of two-electron systems

We present a complex-scaling (CS)-generalized pseudospectral (GPS) method in hyperspherical coordinates (HSC) for \emph{ab initio} and accurate treatment of the electron structure and quantum dynamics of two-electron systems [1]. The GPS method allows non-uniform and optimal spatial discretization of the two-electron Hamiltonian in HSC with the use of only a very modest number of grid points. The procedure is applied for the precision calculation of the energies and widths of doubly-excited Rydberg resonance states as well as the ionization rates of He atoms in intense dc fields. [1] J.~Heslar and S.~I.~Chu, Phys.\ Rev.\ A (submitted).