Journal article

Publication year: 2003

Pages: 421-435

Journal: The Astrophysical Journal: Supplement Series

Volume number: 147

Issue number: 2

ISSN: 0067-0049

Open access status: Green

DOI Link: https://doi.org/10.1086/375688

Publisher: American Astronomical Society

Abstract: 
We have measured dielectronic recombination (DR) resonance strengths and energies for carbon-like Fe XXI forming Fe XX and for boron-like Fe XXII forming Fe XXI via N = 2 --> N' = 2 core excitations. All measurements were carried out using the heavy-ion Test Storage Ring at the Max-Planck-Institute for Nuclear Physics in Heidelberg, Germany. We have also calculated these resonance strengths and energies using three independent, state-of-the-art perturbative techniques: a multiconfiguration Breit-Pauli (MCBP) method using the code AUTOSTRUCTURE, a multiconfiguration Dirac-Fock (MCDF) method, and a relativistic configuration interaction method using the Flexible Atomic Code (FAC). Overall, reasonable agreement is found between our experimental results and our theoretical calculations. The most notable discrepancies tend to occur for relative collision energies less than or similar to 3 eV. We have used our measured 2 --> 2 results to produce Maxwellian-averaged rate coefficients for Fe XXI and Fe XXII. Our experimentally derived rate coefficients are estimated to be accurate to better than approximate to 20% both for Fe XXI at k(B)T(e) > 0.5 eV and for Fe XXII at k(B)T(e) > 0.001 eV. For these results, we provide fits that are accurate to better than 0.5% for Fe XXI at 0.001 eV less than or equal to k(B)T(e) less than or equal to 10, 000 eV and for Fe XXII at 0.02 eV less than or similar to k(B)T(e) less than or equal to 10, 000 eV. Our fitted rate coefficients are suitable for ionization balance calculations involving Fe XXI and Fe XXII in photoionized plasmas. Previous published Burgess formula and LS-coupling calculations are in poor agreement with our experimentally derived rate coefficients. None of these published calculations reliably reproduce the magnitude or temperature dependence of our experimental results. Our previously published Fe XXI MCDF results are in good agreement with our experimental results for k(B)T(e) greater than or similar to 0.07 eV. For both ions in this temperature range our new MCBP, MCDF, and FAC results are in excellent agreement with our experimentally derived rate coefficient.

Harvard Citation style: Savin, D., Kahn, S., Gwinner, G., Grieser, M., Repnow, R., Saathoff, G., et al. (2003) Dielectronic Recombination of Fe XXI and Fe XXII via N = 2→N' = 2 Core Excitations, The Astrophysical Journal: Supplement Series, 147(2), pp. 421-435. https://doi.org/10.1086/375688

APA Citation style: Savin, D., Kahn, S., Gwinner, G., Grieser, M., Repnow, R., Saathoff, G., Schwalm, D., Wolf, A., Müller, A., Schippers, D., Závodszky, P., Chen, M., Gorczyca, T., Zatsarinny, O., & Gu, M. (2003). Dielectronic Recombination of Fe XXI and Fe XXII via N = 2→N' = 2 Core Excitations. The Astrophysical Journal: Supplement Series. 147(2), 421-435. https://doi.org/10.1086/375688