Recombination and electron impact excitation rate coefficients for S XV AND S XVI
2012 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 754, no 2, 86- p.Article in journal (Refereed) Published
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.
atomic data, atomic processes, plasmas
Research subject Physics
IdentifiersURN: urn:nbn:se:su:diva-75369DOI: 10.1088/0004-637X/754/2/86ISI: 000306666700007OAI: oai:DiVA.org:su-75369DiVA: diva2:516120