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Experimental dielectronic recombination rate coefficientsfor Na-like S VI and Na-like Ar VIII
Stockholm University, Faculty of Science, Department of Physics. (Atomic Physics)
Department of Physics, Marmara University, 81040 Istanbul, Turkey.
Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
Stockholm University, Faculty of Science, The Manne Siegbahn Laboratory .
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2009 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 498, 909-914 p.Article in journal (Refereed) Published
Abstract [en]

Aims. Absolute recombination rate coefficients for two astrophysically relevant Na-like ions are presented.Methods. Recombination rate coefficients of S vi and Ar viii are determined from merged-beam type experiments at the CRYRINGelectron cooler. Calculated rate coefficients are used to account for recombination into states that are field-ionized and therefore notdetected in the experiment.Results. Dielectronic recombination rate coefficients were obtained over an energy range covering Δ n = 0 core excitations. ForNa-like Ar a measurement was also performed over the Δn = 1 type of resonances. In the low-energy part of the Ar viii spectrum,enhancements of more than one order of magnitude are observed as compared to the calculated radiative recombination. The plasmarecombination rate coefficients of the two Na-like ions are compared with calculated results from the literature. In the 103−104 Krange, large discrepancies are observed between calculated plasma rate coefficients and our data. At higher temperatures, above105 K, in the case of both ions our data is 30% higher than two calculated plasma rate coefficients, other data from the literaturehaving even lower values.Conclusions. Discrepancies below 104 K show that at such temperatures even state-of-the-art calculations yield plasma rate coefficientsthat have large uncertainties. The main reason for these uncertainties are the contributions from low-energy resonances, whichare difficult to calculate accurately.

Place, publisher, year, edition, pages
2009. Vol. 498, 909-914 p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-33223DOI: 10.1051/0004-6361/200911799ISI: 000266121800027OAI: oai:DiVA.org:su-33223DiVA: diva2:282742
Available from: 2009-12-21 Created: 2009-12-21 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Electron - Ion Recombination Studies of Astrophysically Relevant Ions: Storage Ring and Electron Beam Ion Trap Based Measurements
Open this publication in new window or tab >>Electron - Ion Recombination Studies of Astrophysically Relevant Ions: Storage Ring and Electron Beam Ion Trap Based Measurements
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis contains experimental work that was performed at two state-of-the art devices for electron-ion collision physics, at a heavy-ion storage ring and at an Electron Beam Ion Trap. As a result, absolute recombination rate coefficients for H-like Si, He-like Si, Be-like Si, and Na-like Si, as well as Be-like Ne, Na-like S and Na-like Ar are reported over a wide energy range from μeV to keV. The experimentally derived recombination spectra are compared with results of Many Body Perturbation Theory calculations and AUTOSTRUCTURE calculations. Furthermore, the effect of external electric fields on the recombination rate is investigated for two Na-like ions, and a strong enhancement of dielectronic recombination into high Rydberg states is observed. Experimental plasma rate coefficients are derived for the studied ions for the first time and are compared with calculated values available in the literature. In the EBIT experiment, a novel extraction method provides complete charge state spectra of the ions for every extraction. Absolute DR rate coefficients for both H-like Si and He-like Si are obtained from the same measurement. Comparison with recorded X-ray spectra enables the separation of the photon spectra arising from charge-changing and charge-preserving reactions and facilitates the extraction of electron impact excitation rate coefficients.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2009. 150 p.
Keyword
atomic processes, electron-ion recombination, plasma
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-33254 (URN)978-91-7155-989-0 (ISBN)
Public defence
2010-01-29, sal FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 14:30 (English)
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Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 6: Submitted. Paper 7: Submitted. Available from: 2010-01-07 Created: 2009-12-21 Last updated: 2010-01-08Bibliographically approved

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Orban, IstvanKällberg, AndersSimonsson, AnsgarAndler, GuillermoPaál, AndreasBlom, MikaelLöfgren, PatrikSchuch, Reinhold
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