Journal
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
Volume 188, Issue 1, Pages 32-45Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0067-0049/188/1/32
Keywords
atomic data; atomic processes
Categories
Funding
- NASA [NNX09AB63G]
- United States National Science Foundation [PHY-0244470]
- NASA [120931, NNX09AB63G] Funding Source: Federal RePORTER
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New improved calculations are reported for transition probabilities and electron impact excitation collision strengths for the astrophysically important lines in S II. The collision strengths have been calculated in the close-coupling approximation using the B-spline Breit-Pauli R-matrix method. The multiconfiguration Hartree-Fock method with term-dependent non-orthogonal orbitals is employed for an accurate representation of the target wave functions. The close-coupling expansion includes 70 bound levels of S II covering all possible terms of the ground 3s(2)3p(3) and singly excited 3s3p(4), 3s(2)3p(2)3d, 3s(2)3p(2)4s, and 3s(2)3p(2)4p configurations. The present calculations are more extensive than previous ones, leading to a total 2415 transitions between fine-structure levels. The effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities and these are tabulated for all fine-structure transitions at electron temperatures in the range from 5000 to 100,000 K. The present results are compared with a variety of other close-coupling calculations and available experimental data. There is an overall good agreement with the recent 18-state calculations by Ramsbottom, Bell, & Stafford and with the 19-state calculations by Tayal for the most part, but some significant differences are also noted for some transitions.
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