A package for the ab-initio calculation of one- and two-photon cross sections of two-electron atoms, using a CI B-splines method Original Research Article

A package is presented for the fully ab-initio calculation of one- and two-photon ionization cross sections for two-electron atomic systems (H−, He, Mg, Ca, …) under strong laser fields, within lowest-order perturbation theory (LOPT) and in the dipole approximation. The atomic structure is obtained through configuration interaction (CI) of antisymmetrized two-electron states expanded in a B-spline finite basis. The formulation of the theory and the relevant codes presented here represent the accumulation of work over the last ten years [1–11,13–15]. Extensions to more than two-photon ionization is straightforward. Calculation is possible for both the length and velocity form of the laser–atom interaction operator. The package is mainly, written in standard FORTRAN language and uses the publicly available libraries SLATEC, LAPACK and BLAS.