Radiative transition rates and collision strengths for Si II

M.A. Bautista, Missing Quinet, P. Palmeri, N.R. Badnell, J. Dunn, N. Arav

Research output: Contribution to journalArticle

19 Citations (Scopus)

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.
Original languageEnglish
Pages (from-to)1527-1537
Number of pages10
JournalAstronomy and Astrophysics
Volume508
DOIs
Publication statusPublished - 4 Nov 2009

Fingerprint

collision
collisions
electron
matrix methods
electron impact
approximation
Maxwell-Boltzmann density function
matrix
splines
rate
electron scattering
fine structure
method
electron energy
orbits
optimization
ion
configurations
excitation
energy

Keywords

  • atomic data
  • atomic processes
  • line formation
  • quasars
  • absorption lines
  • Sun abundances
  • ISM atoms

Cite this

Bautista, M.A. ; Quinet, Missing ; Palmeri, P. ; Badnell, N.R. ; Dunn, J. ; Arav, N. / Radiative transition rates and collision strengths for Si II. In: Astronomy and Astrophysics. 2009 ; Vol. 508. pp. 1527-1537.
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Radiative transition rates and collision strengths for Si II. / Bautista, M.A.; Quinet, Missing; Palmeri, P.; Badnell, N.R.; Dunn, J.; Arav, N.

In: Astronomy and Astrophysics, Vol. 508, 04.11.2009, p. 1527-1537.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Radiative transition rates and collision strengths for Si II

AU - Bautista, M.A.

AU - Quinet, Missing

AU - Palmeri, P.

AU - Badnell, N.R.

AU - Dunn, J.

AU - Arav, N.

PY - 2009/11/4

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N2 - 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.

AB - 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.

KW - atomic data

KW - atomic processes

KW - line formation

KW - quasars

KW - absorption lines

KW - Sun abundances

KW - ISM atoms

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