PHOTOIONIZATION CROSS SECTIONS (Updates: Nahar) )

The ab initio calculations are carried out in the close coupling approximation using the R-matrix method as employed in the Opacity Project , and the Iron Project .

The high-energy cross sections, including inner-shell ionization, are complemented by Relativistic Distorted Wave calculations using a Dirac-Fock treatment (Zhang 1995).

The data are available for all atoms and ions with Z=1-14,16,18,20,26 from

**** TOPbase -- WWW interface at NASA GSFC (U.S. Site) ****

or via telnet from heasarc.gsfc.nasa.gov/topbase, and also from TOPBASE. The photoionization cross sections for the low ionization stages of Fe and other heavy elements are being recalculated to higher accuracy (see RECENT PUBLICATIONS 1995 - ).

Owing to their astrophysical importance but intensive computational requirements, the calculations for Fe I, II, III, IV, V are being carried out by the OSU group. The new radiative calculations for Fe I and Fe II differ greatly from the earlier OP data. For example, the recently calculated photoionization cross sections for the ground state of Fe I are up to 3 orders of magnitude higher than the data currently available, the Fe II up to an order of magnitude higher, and Fe III up to a factor of five lower.

We have NOT replaced these data in TOPBASE yet (in general, the data for Fe I - V that is currently in TOPBASE is not accurate).

Fe I : "Photoionization of Neutral Iron", J.Phys.B: Atom. Molec. Opt. Phys. Letters 28, L173-L179 (1995), Manuel A. Bautista and A.K. Pradhan.

Fe II: Nahar and Pradhan,J.Phys.B,27,429,1994.

Fe III: ``Photoionization Cross Sections And Oscillator Strengths For Fe III", Phys.Rev.A 53, 1545 (1996), Sultana N. Nahar.

Fe IV: ``Atomic data from the Iron Project.XXVI. Photoionization Cross Sections and Oscillator Strengths for Fe IV", Astron. Astrophys. (in press), Manuel A. Bautista & Anil K. Pradhan.

Fe V: Atomic data from the Iron Project. XVI. Photoionization cross sections and oscillator strengths for Fe V", Astron.Astrophys. suppl. ser. 119, 105 (1996), Manuel A. Bautista.

For several other elements, more accurate and detailed photoionization calculations than the OP data are in progress as part of the e+ion RECOMBINATION calculations. These are precisely consistent with the new recombination rates; both sets of data may be obtained for a number of ions from Sultana Nahar, including individual state-specific partial photoionization cross sections and recombination rates.

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Revised: 1999 Dec. 1