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Radiative transition rates and collision strengths for Si II

Bautista, M.A. and Quinet, Missing and Palmeri, P. and Badnell, N.R. and Dunn, J. and Arav, N. (2009) Radiative transition rates and collision strengths for Si II. Astronomy and Astrophysics, 508. pp. 1527-1537. ISSN 0004-6361

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    Abstract

    Aims. This work reports on radiative transition rates and electron impact excitation collision strengths for levels of the 3s23p, 3s3p2, 3s24s, and 3s23d configurations of . Methods. The radiative data were computed using the Thomas-Fermi-Dirac-Amaldi central potential, but with the modifications introduced by Bautista (2008) that account for the effects of electron-electron interactions. We also introduce new schemes for the optimization of the variational parameters of the potential. Additional calculations were carried out with the Relativistic Hartree-Fock and the multiconfiguration Dirac-Fock methods. Collision strengths in LS-coupling were calculated in the close coupling approximation with the R-matrix method. Then, fine structure collision strengths were obtained by means of the intermediate-coupling frame transformation (ICFT) method which accounts for spin-orbit coupling effects. Results. We present extensive comparisons between the results of different approximations and with the most recent calculations and experiments available in the literature. From these comparisons we derive a recommended set of gf-values and radiative transition rates with their corresponding estimated uncertainties. We also study the effects of different approximations in the representation of the target ion on the electron-impact collision strengths. Our most accurate set of collision strengths were integrated over a Maxwellian distribution of electron energies and the resulting effective collision strengths are given for a wide range of temperatures. Our results present significant differences from recent calculations with the B-spline non-orthogonal R-matrix method. We discuss the sources of the differences.

    Item type: Article
    ID code: 26868
    Keywords: atomic data, atomic processes, line formation, quasars, absorption lines, Sun abundances, ISM atoms, Physics, Astronomy and Astrophysics, Space and Planetary Science
    Subjects: Science > Physics
    Department: Faculty of Science > Physics
    Related URLs:
      Depositing user: Miss Leonie Airley
      Date Deposited: 19 Aug 2010 14:44
      Last modified: 05 Sep 2014 05:58
      URI: http://strathprints.strath.ac.uk/id/eprint/26868

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