Jo. Andersen et L. Veseth, MANY-BODY CALCULATION OF TOTAL AND PARTIAL PHOTOIONIZATION CROSS-SECTIONS IN ATOMIC NITROGEN, Physica scripta. T, 50(1), 1994, pp. 13-18
Polarizabilities and photoionization cross sections are computed for t
he S-4(o) ground state of atomic nitrogen. The present method is based
on the use of basis sets and on an integral equation (dispersion rela
tion) that relates the real polarizability on the imaginary frequency
axis to the photoionization cross section. Many-body perturbation theo
ry is used to compute the polarization and the perturbation expansion
is complete to second order in the Coulomb interaction. Hence, there i
s a comprehensive inclusion of correlation effects in our calculations
. Comparison with other theory and experiment is made.