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DIELECTRONIC RECOMBINATION OF Na-LIKE S AND Na-LIKE Ar IN THE PRESENCE OF EXTERNAL FIELDS
Stockholm University, Faculty of Science, Department of Physics. (Atomic Physics)
Stockholm University, Faculty of Science, Department of Physics. (Atomic Physics)
Stockholm University, Faculty of Science, Department of Physics. (Atomic Physics)
2009 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 694, no 1, 354-358 p.Article in journal (Refereed) Published
Abstract [en]

Recombination rate coefficients for two astrophysically relevant Na-like ions, S5+ and Ar7+, were derived frommeasurements at the electron cooler device of the CRYRING heavy-ion storage ring. Additionally, the enhancementof dielectronic recombination (DR) by external fields was studied for these ions. Motional electric fields wereinduced over the electron–ion interaction region by tilting the magnetic field that guides the electrons on thetrajectory of the circulating ions. Field ionization at the dipole magnet prevented the detection of ions recombinedinto high Rydberg states. By comparing integrated areas of the recombination spectra over the field-affected range,enhancement factors of up to 1.9 and 2 were observed in the case of S5+ and Ar7+, for the maximum appliedfields of ∼184 V cm−1 and ∼172 V cm−1, respectively. Saturation was not reached and at higher fields even higherenhancements are to be expected. Plasma DR rate coefficients were obtained from the experimental spectra recordedat different field strengths. For the highest applied fields, increasing enhancement of the plasma DR rates was foundwith higher temperatures, reaching up to ∼42% and ∼73% at 106 K, in the case of S5+ and Ar7+, respectively.

Place, publisher, year, edition, pages
2009. Vol. 694, no 1, 354-358 p.
Keyword [en]
atomic data – atomic processes – magnetic fields – plasmas
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-33230DOI: 10.1088/0004-637X/694/1/354ISI: 000264291700035OAI: oai:DiVA.org:su-33230DiVA: diva2:282755
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)
Opponent
Supervisors
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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