ELECTRON-ION RECOMBINATION OF Fe XII FORMING Fe XI: LABORATORY MEASUREMENTS AND THEORETICAL CALCULATIONS

Journal Article · Sun Jul 01 00:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/753/1/57· OSTI ID:22036929

Novotny, O; Hahn, M; Lestinsky, M; Savin, D W ^[1]; Badnell, N R ^[2]; Bernhardt, D; Mueller, A; Schippers, S ^[3]; Grieser, M; Krantz, C; Repnow, R; Wolf, A ^[4]

---

1. Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
2. Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom)
3. Institut fuer Atom- und Molekuelphysik, Justus-Liebig-Universitaet Giessen, D-35392 Giessen (Germany)
4. Max Planck Institute for Nuclear Physics, 69117 Heidelberg (Germany)

We have measured electron-ion recombination for Fe XII forming Fe XI using a merged-beam configuration at the heavy-ion storage ring TSR located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. The measured merged-beam recombination rate coefficient (MBRRC) for collision energies from 0 to 1500 eV is presented. This work uses a new method for determining the absolute MBRRC based on a comparison of the ion beam decay rate with and without the electron beam on. For energies below 75 eV, the spectrum is dominated by dielectronic recombination (DR) resonances associated with 3s {yields} 3p and 3p {yields} 3d core excitations. At higher energies, we observe contributions from 3 {yields} N' and 2 {yields} N' core excitation DR. We compare our experimental results to state-of-the-art multi-configuration Breit-Pauli (MCBP) calculations and find significant differences, both in resonance energies and strengths. We have extracted the DR contributions from the measured MBRRC data and transformed them into a plasma recombination rate coefficient (PRRC) for temperatures in the range of 10{sup 3}-10{sup 7} K. We show that the previously recommended DR data for Fe XII significantly underestimate the PRRC at temperatures relevant for both photoionized plasmas (PPs) and collisionally ionized plasmas (CPs). This is contrasted with our MCBP PRRC results, which agree with the experiment to within 30% at PP temperatures and even better at CP temperatures. We find this agreement despite the disagreement shown by the detailed comparison between our MCBP and experimental MBRRC results. Last, we present a simple parameterized form of the experimentally derived PRRC for easy use in astrophysical modeling codes.

• OSTI ID: 22036929
• Journal Information: Astrophysical Journal, Vol. 753, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASTROPHYSICS
COMPUTERIZED SIMULATION
ELECTRON BEAMS
ELECTRON-ION COLLISIONS
EMISSION SPECTRA
EV RANGE
EXCITATION
GALAXY NUCLEI
HEAVY IONS
ION BEAMS
IRON IONS
PHOTOIONIZATION
PLASMA
RECOMBINATION
RESONANCE
TSR STORAGE RING
X-RAY GALAXIES