Ma. Bautista et Ak. Pradhan, ATOMIC DATA FROM THE IRON PROJECT .26. PHOTOIONIZATION CROSS-SECTIONSAND OSCILLATOR-STRENGTHS FOR FEIV, Astronomy & Astrophysics. Supplement series, 126(2), 1997, pp. 365-371
Photoionization cross sections and dipole transition probabilities for
the astrophysically important iron ion Fe IV are presented. The compu
tations were carried out in the close coupling approximation using the
R-matrix method including 31 LS terms with multiplicity (2S + 1) = 3
and 5 of the target ion Fe V. All quartets and sextet bound states of
Fe IV with n less than or equal to 10 and L less than or equal to 8 ar
e considered. The results include 746 LS bound states, dipole oscillat
or strengths for 34 635 LS transitions, and, for all bound states, det
ailed photoionization cross sections with extensive resonance structur
es. These data differ significantly in many cases from the earlier dat
a calculated under the Opacity Project and other theoretical calculati
ons. In particular, the new cross section for the S-6 ground state of
Fe IV exhibits a large resonance near the threshold that is not presen
t in previous calculations and is likely to affect the effective photo
ionization rate significantly. The autoionizing state that corresponds
to that resonance as well as the Rydberg series to which it belongs a
re identified through supplementary close coupling calculations.