PHOTOIONIZATION CROSS-SECTION CALCULATION OF ATOMIC TUNGSTEN

A photoionization cross-section calculation of atomic tungsten is performed in the formalism of many-body perturbation theory for photon energies ranging from the ionization threshold of tungsten to 150 eV. Nonrelativistic orbitals are used in the basis set and relativistic corrections are included. We consider excitations from the 4f, 5s, 5p, 5d, and 6s subshells. The effects of the strong 5p(6)5d4-->5p(5)5d5 and 4f(14)5d4-->4f(13)5d5 transitions are included as resonant contributions to the 5d partial cross section. Our results indicate that the 5d partial cross section dominates the total cross section below 100 eV.