Astronomy & Astrophysics

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Issue		A&A Volume 492, Number 1, December II 2008
Page(s)		265 - 275
Section		Atomic, molecular, and nuclear data
DOI		10.1051/0004-6361:200810834
Published online		27 October 2008

A&A 492, 265-275 (2008)
DOI: 10.1051/0004-6361:200810834

Electron-ion recombination for $\ion{viii}$ forming $\ion{vii}$ and $\ion{ix}$ forming $\ion{viii}$ : measurements and theory

E. W. Schmidt¹, S. Schippers¹, D. Bernhardt¹, A. Müller¹, J. Hoffmann², M. Lestinsky^{2, 3}, D. A. Orlov², A. Wolf², D. V. Lukić³, D. W. Savin³, and N. R. Badnell⁴

¹ Institut für Atom- und Molekülphysik, Justus-Liebig-Universität, Leihgesterner Weg 217, 35392 Giessen, Germany http://www.uni-giessen.de/cms/iamp
e-mail: eike.w.schmidt@iamp.physik.uni-giessen.de
² Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany http://www.mpi-hd.mpg.de/ion-storage/
³ Columbia Astrophysics Laboratory, Columbia University, 550 West 120th, New York, NY 10027, USA http://www.astro.columbia.edu/ savin/
⁴ Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK http://amdpp.phys.strath.ac.uk/

Received 20 August 2008 / Accepted 9 October 2008

Abstract
The photorecombination rate coefficients of potassium-like $\ion{viii}$ ions forming calcium-like $\ion{vii}$ and of argon-like $\ion{ix}$ forming potassium-like $\ion{viii}$ were measured by employing the merged electron-ion beams method at the Heidelberg heavy-ion storage-ring TSR. New theoretical calculations with the AUTOSTRUCTURE code were carried out for dielectronic recombination (DR) and trielectronic recombination (TR) for both ions. We compare these experimental and theoretical results and also compare with previously recommended rate coefficients. The DR and TR resonances were experimentally investigated in the electron-ion collision energy ranges 0–120 eV and 0–151 eV for $\ion{viii}$ and $\ion{ix}$ . Experimentally derived $\ion{viii}$ and $\ion{ix}$ DR + TR plasma rate coefficients are provided in the temperature range $k_{\rm B}T=0.2$ to $1000~{\rm eV}$ . Their uncertainties amount to < $\pm26\%$ and < $\pm35\%$ at a 90% confidence level for $\ion{viii}$ and $\ion{ix}$ , respectively.

Key words: atomic data -- atomic processes -- plasmas -- galaxies: active -- galaxies: nuclei -- X-rays: galaxies

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Electron-ion recombination for forming and forming : measurements and theory

Electron-ion recombination for $\ion{viii}$ forming $\ion{vii}$ and $\ion{ix}$ forming $\ion{viii}$ : measurements and theory