log gf values for astrophysically important transitions Fe II

¹ School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN, UK
e-mail: a.hibbert@qub.ac.uk
² Indian Maritime University, Kolkata Campus, P-19, Taratala Road, 700088 Kolkata, INDIA

Received: 25 September 2013
Accepted: 31 October 2013

Abstract

Aims. In a recent measurement, Meléndez & Barbuy (2009, A&A, 497, 611) report accurate log  gf values for 142 important astrophysical lines with wavelengths in the range 4000 Å to 8000 Å. Their results include both solar and laboratory measurements. In this paper, we describe a theoretical study of these lines.

Methods. The CIV3 structure codes, combined with our “fine-tuning” extrapolation process, are used to undertake a large-scale CI calculation involving the lowest 262 fine-structure levels belonging to the 3d⁶4s, 3d⁷, 3d⁵4s², 3d⁶4p, and 3d⁵4s4p configurations.

Results. We find that many of the 142 transitions are very weak intercombination lines. Other transitions are weak because the dominant configurations in the two levels differ by two orbitals.

Conclusions. The comparison between our log gf values and the experimental values generally shows good agreement for most of these transitions, with our theoretical values agreeing slightly more closely with the solar than with the laboratory measurements. A detailed analysis of the small number of transitions for which the agreement between theory and experiment is not as good shows that such disagreements largely arise from severe cancellation due to CI mixing.