PHOTOIONIZATION OF NEUTRAL IRON

Accurate calculations are reported for the photoionization of the grou nd and the excited states of Fe I with an extensive coupled channel ex pansion using the R-matrix method. A total of 52 LS terms of the core ion Fe II dominated by configurations 3d(6)4s, 3d(7), 3d(6)4p, 3d(5)4s (2), 3d(5)4s4p are included; these eigenstates thereby account for the photoionization of the outer 4s subshell as well as the open inner 3d subshell of the ground state 3d(6)4s(2)(D-5) of Fe I. The coupling of all relevant photoionization channels give rise to extensive autoioni zation structures and ensure that no large and sharp discontinuity at the 3d inner-shelf ionization edge is present. The new results differ by up to several orders of magnitude from earlier data in central fiel d type approximations that are currently employed in plasma modelling of astrophysical and laboratory sources.