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Electron-ion recombination of Be-like C, N, and O
Stockholm University, Faculty of Science, Department of Physics.
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2005 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 442, no 2, 757-766 p.Article in journal (Refereed) Published
Abstract [en]

The absolute total recombination reaction rate coefficients for Be-like C, N, and O have been measured using the CRYRING storage ring and compared with the results from distorted-wave theory. For the theory results, it is found that shifts to NIST energy values for the core excited energies of the recombining system are not sufficient to accurately match all of the resonance positions and heights at lower energies. These theory results represent the quality of most archived theory DR data. The accurate calculation of these low energy resonances still presents a significant challenge to theory. In addition, trielectronic recombination resonances, associated with the formation of triply excited states during recombination, have been observed in the total recombination reaction rate coefficient spectra of and . Finally, we construct a dielectronic recombination Maxwellian rate coefficient from the experimental results for low n resonances, and from the theoretical results for high n resonances. In the case of , the trielectronic recombination resonances have a strong influence on the low temperature Maxwellian rate coefficient. Our best hybrid Maxwellian rate coefficient is compared with archived distorted-wave theory data, and is found to be in reasonable agreement, even at the low temperatures.

Place, publisher, year, edition, pages
2005. Vol. 442, no 2, 757-766 p.
Keyword [en]
atomic -- molecular and nuclear data
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-25861DOI: 10.1051/0004-6361:20040559OAI: diva2:200701
Part of urn:nbn:se:su:diva-95Available from: 2004-04-05 Created: 2004-04-05 Last updated: 2010-08-09Bibliographically approved
In thesis
1. Recombination and ionization of astrophysically abundant ions
Open this publication in new window or tab >>Recombination and ionization of astrophysically abundant ions
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The electron-ion recombination and electron-impact ionization of several astrophysically abundant C, N, O, and Ni ions have been investigated using the synchrotron storage ring CRYRING. The recombination rate coefficients predominanty used in the analyses of emission line spectra and for ionization balance calculations are determined from isoelectronic fits and extrapolations of theoretical and limited experimental results available from the literature. The rate coefficients reported by various authors differ by an order of magnitude for various ion species. For low temperature plasmas(<104 K), the available information on resonant recombination rate coefficients is even more limitied and, unfortunately, most available data has been determined from LS coupling calculations, which can have adverse effects on recombination rates due to the mistreatment of autoionizing states.

For ions of C, N, and O, the production of metastable states complicates the experimental rate coefficient determinations. Some attempts have been made in this work to utilize both recombination and electron-impact ionization in estimating the metastable ion beam fractions present. Other metastable fractions have been determined by comparing the experimental recombination spectra to intermediate coupling calculations. Some of the absolute recombination rate coefficients reported in this work are given for the first time while many others vastly improve the spectral resolution of previous experiments, allowing for a more detailed study of the low energy resonances which contribute to the resonant recombination rate coefficient at low plasma electron temperatures. This increased resolution has also lead to the observation of trielectronic recombination resonances which greatly influence low temperature recombinaion rates in some ions.

Place, publisher, year, edition, pages
Stockholm: Fysikum, 2004. 60 p.
atomic data, plasma
National Category
Atom and Molecular Physics and Optics
urn:nbn:se:su:diva-95 (URN)91-7265-839-8 (ISBN)
Public defence
2004-04-26, sal FD5, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00
Available from: 2004-04-05 Created: 2004-04-05Bibliographically approved

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Schuch, Reinhold
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