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Determination of the recombination rate coefficients for Na-like Si IV forming Mg-like Si III
Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
Vise andre og tillknytning
2006 (engelsk)Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 459, nr 1, s. 291-296Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Aims. Absolute, total recombination rate coefficients for Si iv were determined using the CRYRING heavy-ion storage ring.Calculated rate coefficients were used to estimate recombination into states that could not be detected in the experiment becauseof field ionization. Total, as well as separate, radiative and dielectronic plasma recombination rate coefficients were determined.Methods. Stored ions were merged with an expanded electron beam in the electron cooler section of the storage ring. Recombined ionswere separated from the stored ion beam in the first dipole magnet after the electron cooler and were detected with unity efficiency.The absolute radiative and dielectronic recombination rate coefficients were obtained over a center-of-mass energy range of 0−20 eV,covering Δn = 0 core excitations up to the 3s → 3d series limit. The results of an intermediate coupling autostructure calculationwere compared with the experiment. The theoretical results were also used to estimate the contribution to dielectronic recombinationby high Rydberg states, which were not detected because of field ionization. The spectra were convoluted with Maxwell-Boltzmannenergy distributions in the 103−106 K temperature range.Results. The resulting plasma recombination rate coefficients are presented and compared with theoretical results frequently usedfor plasma modeling. In the 103−104 K range, a significant underestimation of the calculated dielectronic recombination plasma ratecoefficients was observed. Above 3 × 104 K, the agreement between our dielectronic recombination plasma rate coefficients and twoof the previously published rate coefficients is better than 20%.Conclusions. The observed differences between the experimental and calculated recombination rate coefficients at low temperaturesreflect the need for benchmarking experiments. Our experimentally-derived rate coefficients can guide the development of bettertheoretical models and lead to more accurately-calculated rate coefficients.

sted, utgiver, år, opplag, sider
2006. Vol. 459, nr 1, s. 291-296
Emneord [en]
atomic data, atomic processes, plasmas
HSV kategori
Identifikatorer
URN: urn:nbn:se:su:diva-12367DOI: 10.1051/0004-6361:20054660OAI: oai:DiVA.org:su-12367DiVA, id: diva2:178887
Tilgjengelig fra: 2009-01-15 Laget: 2009-01-15 Sist oppdatert: 2017-12-13bibliografisk kontrollert
Inngår i avhandling
1. Electron - Ion Recombination Studies of Astrophysically Relevant Ions: Storage Ring and Electron Beam Ion Trap Based Measurements
Åpne denne publikasjonen i ny fane eller vindu >>Electron - Ion Recombination Studies of Astrophysically Relevant Ions: Storage Ring and Electron Beam Ion Trap Based Measurements
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: Department of Physics, Stockholm University, 2009. s. 150
Emneord
atomic processes, electron-ion recombination, plasma
HSV kategori
Forskningsprogram
fysik
Identifikatorer
urn:nbn:se:su:diva-33254 (URN)978-91-7155-989-0 (ISBN)
Disputas
2010-01-29, sal FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 14:30 (engelsk)
Opponent
Veileder
Merknad
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 6: Submitted. Paper 7: Submitted. Tilgjengelig fra: 2010-01-07 Laget: 2009-12-21 Sist oppdatert: 2010-01-08bibliografisk kontrollert

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