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Recombination and electron impact excitation rate coefficients for S XV AND S XVI
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
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2012 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 754, no 2, 86- p.Article in journal (Refereed) Published
Abstract [en]

Recombination and electron impact excitation of S14+ and S15+ ions was measured at the Stockholm refrigerated electron beam ion trap. The collision energy range was 1.4-3 keV, where we covered the KLL, KLM, KLN, and KLO dielectronic recombination resonances resulting in S13+ and S14+ ions. The recombination rates were obtained by detecting the charge state distribution with a newly developed time-of-flight technique. Resonance energies and cross sections calculated within the relativistic many-body perturbation theory for S15+ agree well with the experimental data. The temperature dependent rate coefficients have been extracted from the measured rates and compared with calculations from literature used for studies of collisionally ionized astrophysical plasmas. A good agreement for S15+ was obtained, while the plasma rates for S14+ were 23% lower than the so far published values. In addition to the time-of-flight spectra, the x-ray spectra, produced mainly by photo-recombination and excitation, have been also collected. The combination of these two measurements allowed us to separate the photo-recombination and the excitation spectra, and the excitation rate coefficients for summed intensities with known fractions of S14+ and S15+ ions were extracted.

Place, publisher, year, edition, pages
2012. Vol. 754, no 2, 86- p.
Keyword [en]
atomic data, atomic processes, plasmas
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-75369DOI: 10.1088/0004-637X/754/2/86ISI: 000306666700007OAI: oai:DiVA.org:su-75369DiVA: diva2:516120
Available from: 2012-04-17 Created: 2012-04-17 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Electron - Ion Recombination Data for Plasma Applications: Results from Electron Beam Ion Trap and Ion Storage Ring
Open this publication in new window or tab >>Electron - Ion Recombination Data for Plasma Applications: Results from Electron Beam Ion Trap and Ion Storage Ring
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis contains results of electron-ion recombination processes in atomic ions relevant for plasma applications. The measurements were performed at the Stockholm Refrigerated Electron Beam Ion Trap (R-EBIT) and at the CRYRING heavy-ion storage ring. Dielectronic recombination (DR) cross sections, resonant strengths, rate coefficients and energy peak positions in H-like and He-like S are obtained for the first time from the EBIT measurements. Furthermore, the experimentally obtained DR resonant strengths are used to check the behaviour of a scaling formula for low Z, H-and He-like iso-electronic sequences and to update the fitting parameters. KLL DR peak positions for initially He- to B-like Ar ions are obtained experimentally from the EBIT measurements. Both the results from highly charged sulfur and argon are compared with the calculations performed with a distorted wave approximation.

Absolute recombination rate coefficients of B-like C, B-like Ne and Be-like F ions are obtained for the first time with high energy resolution from storage ring measurements. The experimental results are compared with the intermediate coupling AUTOSTRUCTURE calculations. Plasma rate coefficients of each of these ions are obtained by convoluting the energy dependent recombination spectra with a Maxwell-Boltzmann energy distribution in the temperature range of 103-106 K. The resulting plasma rate coefficients are presented and compared with the calculated data available in literature.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2012. 64 p.
Keyword
Highly charged ions, Atomic processes, Atomic data, Electron-ion recombination, Plasmas
National Category
Physical Sciences Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-75311 (URN)978-91-7447-497-8 (ISBN)
Public defence
2012-05-14, sal FA31, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Accepted. Paper 5: Accepted. Paper 6: Manuscript. Paper 7: Manuscript.

Available from: 2012-04-22 Created: 2012-04-14 Last updated: 2013-08-20Bibliographically approved
2. Interaction of atomic ions with electrons: Recombination rate coefficients for C1+, F5+, Ne5+, S14+,S15+
Open this publication in new window or tab >>Interaction of atomic ions with electrons: Recombination rate coefficients for C1+, F5+, Ne5+, S14+,S15+
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concentrates on electron-ion interaction studies, in particular focusing on dielectronic recombination (DR) of highly charged ions relevant to astrophysics and plasma physics. The measurements were performed at the Stockholm Refrigerated Electron Beam Ion Trap (R-EBIT) and at the CRYRING heavy-ion storage ring. For the R-EBIT measurements a newly developed time-of-flight (TOF) technique for separation of ions and detecting the charge state distribution was utilized. By using ion intensities derived from the TOF spectra as input parameters in the rate equations, energy dependent DR rate coefficients for S15+ and S14+ ions were obtained for the first time. Resonance energies and cross sections calculated within the relativistic many-body perturbation theory for S15+ agree well with the experimental data. In addition to the TOF spectra, the x-ray spectra have been also collected. The combination of these two measurements allows us to separate the photo-recombination and the excitation spectra, from which the excitation rate coefficients for S15+ and S14+ ions were extracted.

From the storage ring measurements absolute recombination rate coefficients for C1+, F5+, and Ne5+ions as a function of electron-ion collision energy were obtained. These were reported for the first time with high energy resolution. The experimental results were compared with results obtained from AUTOSTRUCTURE calculations. Temperature dependent rate coefficients have been also derived for the studied ions and compared with calculations available in the literature.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2012. 71 p.
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-75912 (URN)978-91-7447-529-6 (ISBN)
Public defence
2012-06-11, FB41, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Accepted. Paper 5: Manuscript. Paper 6: Accepted. Paper 7: Manuscript.

Available from: 2012-05-10 Created: 2012-05-03 Last updated: 2013-08-20Bibliographically approved

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