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Session 54 - Ground and Instrumentation Techniques and Catalogs.
Display session, Wednesday, June 12
Tripp Commons,
Emission and absorption lines from Iron ions are of great importance as diagnostics for a large variety of objects and in most wavelength ranges, from the X-ray and extreme UV up to the far IR. The IRON Project is an international collaboration devoted to the study of atomic processes and the calculation of collisional and radiative data for ions of the iron-peak elements for applications in astrophysical and laboratory plasmas. The ab initio atomic calculations are carried out in the close-coupling approximation, using the R-matrix method and a package of codes developed for the Opacity Project and extended to include relativistic effects in the Breit-Pauli approximation. Parameters for many of the atomic processes of importance in astrophysics are calculated: (i) photoionization cross sections, (ii) total e-ion recombination rates including both the radiative and di-electr onic recombination processes, (iii) collision strengths, and (iv) radiative transition probabilities. Selected results will be presented for Fe I, Fe II, Fe III, Fe IV, Fe V, Fe XXII, Fe XXV, and Ni II. Of particular interest are the results for the low ionization stages of Iron: Fe I,II, and III, for which the new photoionization cross sections and corresponding recombination rates, both computed in a self-consistent manner for the first time, differ from the data currently in use in astrophysical models by up to several orders of magnitude. Also, at Ohio State, a parallelized version of the R-matrix codes has been developed for the massively parallel machine Cray T3D, thus enhancing the computational capabilities needed for such extensive calculations. The work is supported partially by the U.S. National Science Foundation (PHY-9421898), the NASA LTSA program (NAGW-3315) and the NASA ADP program (NAS5-32643).
