A&A Supplement Series, Vol. 126, December I 1997, 365-371
Received Febuary 28; accepted March 3, 1997
M.A. Bautista and A.K. Pradhan
Department of Astronomy, The Ohio State University, 174 West 18th Avenue, Columbus, OH 43210-1106, U.S.A.
Photoionization cross sections and dipole
transition probabilities for the astrophysically important iron ion
Fe IV are presented.
The computations 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 
and 
are considered. The results include 746 LS bound states,
dipole oscillator strengths for 34 635 LS transitions,
and, for all bound states, detailed photoionization
cross sections with extensive resonance structures.
These data differ
significantly in many cases from the earlier data calculated under the
Opacity Project and other theoretical calculations.
In particular, the new cross section for the 
ground state of Fe IV
exhibits a large resonance near the threshold that is
not present in previous calculations and is likely to affect the
effective photoionization rate significantly. The autoionizing state
that corresponds
to that resonance as well as the Rydberg series to which it belongs are
identified through supplementary close coupling calculations.
keywords: atomic data -- plasmas -- ultraviolet general