ATOMIC DATA FOR OPACITY CALCULATIONS .15. FE I-IV

Photoexcitation and photoionization processes are examined for ground and excited terms of Fe I, Fe II, Fe III and Fe IV. An LS coupling R-matrix approach is used in a seventeen target term expansion for Fe I, including 3d7, 3d6(5D)4s, 3d6(5D)4p and 3d5(6S)4s2 configurations; and sixteen term expansions for Fe II, Fe III and Fe IV, including 3d6, 3d5 and 3d4 configurations respectively. Data for even and odd LS terms having S less-than-or-equal-to 3; L less-than-or-equal-to 7 and effective principal quantum numbers up to 10 are calculated. Over six thousand term energies and nearly half a million dipole oscillator strengths are calculated. The photoionization cross section is tabulated for all bound terms over a fine mesh of photon energies to elucidate the low-energy resonance structure.