Spectroscopic study of doubly excited states in Mg-likeSi using dielectronic recombination
2007 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, Vol. 40, no 5, 1063-1080 p.Article in journal (Refereed) Published
We present calculated and experimentally derived electron–ion recombinationrate coefficients for Na-like Si IV, recombining into Mg-like Si III, andprovide accurate spectroscopic data for doubly excited states located above theionization threshold of Si III. The experimental recombination rate coefficientswere measured in a merged-beam-type experiment at the heavy-ion storagering CRYRING at the Manne Siegbahn Laboratory in Stockholm. Changing theelectron–ion relative energy from 0 to 20 eV we covered the energy region fromthe first to the third ionization threshold. We find that even for the low-chargedSi2+ ion, a relativistic many-body perturbation theory calculation is necessary,to describe the recombination rate coefficients in the low-energy region, up to1.5 eV, satisfactorily. Doubly excited states, forbidden to form in LS coupling,are responsible for the most prominent dielectronic recombination resonances atlow energies and contribute with 40% to the strength. Several wide resonancesgive rise to a plateau-like formation in the recombination spectrum. A broaderenergy range, up to 6.7 eV, was covered with a non-relativistic many-bodycalculation. This range contains, in addition to 3pn resonances, severalresonances of the type 3dn, with the LS-forbidden 3d2 3F states giving riseto a strong, isolated peak at 2.976 eV. The NIST database lists eleven doublyexcited states of Si III with energy positions deviating considerably from ourdetermination. Since the listed lines are also not fully matching those with thelargest fluorescence yields it must be concluded that they are misidentified.
Place, publisher, year, edition, pages
2007. Vol. 40, no 5, 1063-1080 p.
IdentifiersURN: urn:nbn:se:su:diva-33213DOI: 10.1088/0953-4075/40/5/018ISI: 000244584800021OAI: oai:DiVA.org:su-33213DiVA: diva2:282714