Recombination rate coefficients of Be-like neon
2008 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 489, no 2, 829-835 p.Article in journal (Refereed) Published
Aims. Merged-beam and plasma recombination rate coefficients for Be-likeNe vii were extracted from results of a merged-beam typeexperiment.Methods. The cryring heavy-ion storage ring was used to determine merged-beam recombination rate coefficients for Be-likeNe6+.Recombined Ne5+ ions were separated from the stored beam in the first dipole magnet following the electron-ion interaction region.Field-ionization at this dipole magnet prevented detection of recombination into states with the principal quantum number n > ncutoff =23. To account for the field-ionization effects, results obtained with autostructure calculations were used for recombinationchannels above ncutoff. The merged-beam recombination rate coefficients were then convoluted with Maxwellian electron energydistributions in the 103−3 × 106 K temperature region, to obtain plasma recombination rate coefficients.Results. Good agreement was found between the experimentally derived rate coefficient spectrum and results of the autostructurecalculation. At low energies, several strong dielectronic recombination resonances belonging to the spin-forbidden 2s2p(3PJ)nl seriesdominate the merged-beam spectrum. Recombination through these states dominates at low-temperatures, e.g. at 103 K recombinationthrough these resonances is more than one order of magnitude higher than the radiative recombination rate coefficient. Most data fromthe literature significantly underestimate the low-temperature plasma rate coefficients below 104 K, with only two calculations showingrate coefficients comparable to our results.Strong contributions from trielectronic recombination were found in the merged-beam spectrum of Be-like Ne, associated with doubleexcitation of the Be-likeNe core, during the attachment of the free electron. Calculated trielectronic recombination resonance positionsagree with experimental peaks, however compared to the experiment, the calculation underestimates the strength of trielectronicrecombination.
Place, publisher, year, edition, pages
2008. Vol. 489, no 2, 829-835 p.
atomic data, atomic processes, line: formation, plasmas, Sun: general
IdentifiersURN: urn:nbn:se:su:diva-33244DOI: 10.1051/0004-6361:200810295ISI: 000259601500046OAI: oai:DiVA.org:su-33244DiVA: diva2:282761