The Iron Project: Atomic Data for the Iron Peak Elements

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Session 22 -- Stellar Spectroscopy, Atmospheres, Models, Intrinsic Variables, Theory, Part II
Display presentation, Tuesday, June 13, 1995, 9:20am - 6:30pm

[22.06] The Iron Project: Atomic Data for the Iron Peak Elements

Anil K. Pradhan, Hong Lin Zhang, Jianfang Peng, Sultana N. Nahar, and Manuel A. Bautista (Department of Astronomy, The Ohio State University)

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. We report large-scale computations of photoionization cross sections, transition probabilities and collision strengths, under the auspices of an international collaboration known as the Iron Project devoted to the calculation of accurate atomic data for the Iron peak elements. Selected results are presented for the lower ionization stages of Iron, Fe I-VI. These calculations are carried out in the close coupling approximation using the R-matrix method as developed for the Opacity Project and further extended to the Iron Project, including relativistic effects. It is found, for example, that existing atomic data for these ions is considerably inaccurate; the new Fe~I photoionization cross sections are up to 3 orders of magnitude higher, and those of Fe~II up to an order of magnitude, and Fe~V up to a factor of 5. We have also obtained partial photoionization cross sections for these ions which are necessary for non-LTE spectral modeling. The calculations for the collisional data include collision strengths and rate coefficients for 10,011 transitions in Fe~II and 23,871 transitions in Fe~III. Work on the Collision strengths for Fe~IV-VI, Co~II-III, and Ni~II-III is in progress. Results on total electron-ion recomnination rates obtained employing the new unified treatment and applications to the ionization balance will be presented. \\ $\star$ Work supported by NSF grant PHY-9421898 and NASA grant NAS5-32643.

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