R-matrix electron-impact excitation data for B-like Si and its application in cool stars

G.Y. Liang, A.D. Whiteford, N.R. Badnell

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

We present the results of an intermediate coupling frame-transformation R-matrix calculation for the electron-impact excitation of Si9+. The target and close-coupling expansions are both taken to be the 125 fine-structure levels (58 LS terms) belonging to the configurations 2sx2py (x+y = 3) and 2s2p3l (+ = 2, l = s, p, and d). Due to the additional resonances included in our calculation, we find significant differences at low temperatures with the widely used n = 2 2 excitation rates, also obtained with the R-matrix method, as well as with the n = 2 3 excitation rates calculated by using the distorted wave (DW) approximation. We present a list of prominent transition lines and comparisons with SERTS and Hinode/EIS EUV spectra of the solar corona, SUMER observations for the quiet sun, as well as Chandra LETG and Rocket soft X-ray spectra of the Procyon corona and solar flares, respectively. Line emissivities of some transitions are enhanced up to 40% when compared with those obtained from using the previous atomic data at the same electron density (1.6 109 cm-3) and temperature (1.3 106 K). The comparison with Chandra LETG observation of Procyon reveals that the 3s-2p line flux was significantly underestimated (by a factor of 4-5) in previous analyses. Some EUV and soft X-ray emission line ratios are -sensitive and -insensitive. Estimated electron densities from them shift downwards due to the new resonant-enhanced excitation data used in the present modelling.
LanguageEnglish
Pages943-954
Number of pages11
JournalAstronomy and Astrophysics
Volume499
Issue number3
DOIs
Publication statusPublished - 1 Jun 2009

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cool stars
electron density
electron impact
corona
electron
matrix
emissivity
excitation
solar corona
solar flares
rockets
matrix methods
lists
coronas
flares
modeling
sun
x rays
temperature
fine structure

Keywords

  • atomic data
  • atomic processes
  • plasmas
  • stars
  • coronae
  • X-rays
  • ultraviolet
  • solar system

Cite this

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abstract = "We present the results of an intermediate coupling frame-transformation R-matrix calculation for the electron-impact excitation of Si9+. The target and close-coupling expansions are both taken to be the 125 fine-structure levels (58 LS terms) belonging to the configurations 2sx2py (x+y = 3) and 2s2p3l (+ = 2, l = s, p, and d). Due to the additional resonances included in our calculation, we find significant differences at low temperatures with the widely used n = 2 2 excitation rates, also obtained with the R-matrix method, as well as with the n = 2 3 excitation rates calculated by using the distorted wave (DW) approximation. We present a list of prominent transition lines and comparisons with SERTS and Hinode/EIS EUV spectra of the solar corona, SUMER observations for the quiet sun, as well as Chandra LETG and Rocket soft X-ray spectra of the Procyon corona and solar flares, respectively. Line emissivities of some transitions are enhanced up to 40{\%} when compared with those obtained from using the previous atomic data at the same electron density (1.6 109 cm-3) and temperature (1.3 106 K). The comparison with Chandra LETG observation of Procyon reveals that the 3s-2p line flux was significantly underestimated (by a factor of 4-5) in previous analyses. Some EUV and soft X-ray emission line ratios are -sensitive and -insensitive. Estimated electron densities from them shift downwards due to the new resonant-enhanced excitation data used in the present modelling.",
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author = "G.Y. Liang and A.D. Whiteford and N.R. Badnell",
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R-matrix electron-impact excitation data for B-like Si and its application in cool stars. / Liang, G.Y.; Whiteford, A.D.; Badnell, N.R.

In: Astronomy and Astrophysics, Vol. 499, No. 3, 01.06.2009, p. 943-954.

Research output: Contribution to journalArticle

TY - JOUR

T1 - R-matrix electron-impact excitation data for B-like Si and its application in cool stars

AU - Liang, G.Y.

AU - Whiteford, A.D.

AU - Badnell, N.R.

PY - 2009/6/1

Y1 - 2009/6/1

N2 - We present the results of an intermediate coupling frame-transformation R-matrix calculation for the electron-impact excitation of Si9+. The target and close-coupling expansions are both taken to be the 125 fine-structure levels (58 LS terms) belonging to the configurations 2sx2py (x+y = 3) and 2s2p3l (+ = 2, l = s, p, and d). Due to the additional resonances included in our calculation, we find significant differences at low temperatures with the widely used n = 2 2 excitation rates, also obtained with the R-matrix method, as well as with the n = 2 3 excitation rates calculated by using the distorted wave (DW) approximation. We present a list of prominent transition lines and comparisons with SERTS and Hinode/EIS EUV spectra of the solar corona, SUMER observations for the quiet sun, as well as Chandra LETG and Rocket soft X-ray spectra of the Procyon corona and solar flares, respectively. Line emissivities of some transitions are enhanced up to 40% when compared with those obtained from using the previous atomic data at the same electron density (1.6 109 cm-3) and temperature (1.3 106 K). The comparison with Chandra LETG observation of Procyon reveals that the 3s-2p line flux was significantly underestimated (by a factor of 4-5) in previous analyses. Some EUV and soft X-ray emission line ratios are -sensitive and -insensitive. Estimated electron densities from them shift downwards due to the new resonant-enhanced excitation data used in the present modelling.

AB - We present the results of an intermediate coupling frame-transformation R-matrix calculation for the electron-impact excitation of Si9+. The target and close-coupling expansions are both taken to be the 125 fine-structure levels (58 LS terms) belonging to the configurations 2sx2py (x+y = 3) and 2s2p3l (+ = 2, l = s, p, and d). Due to the additional resonances included in our calculation, we find significant differences at low temperatures with the widely used n = 2 2 excitation rates, also obtained with the R-matrix method, as well as with the n = 2 3 excitation rates calculated by using the distorted wave (DW) approximation. We present a list of prominent transition lines and comparisons with SERTS and Hinode/EIS EUV spectra of the solar corona, SUMER observations for the quiet sun, as well as Chandra LETG and Rocket soft X-ray spectra of the Procyon corona and solar flares, respectively. Line emissivities of some transitions are enhanced up to 40% when compared with those obtained from using the previous atomic data at the same electron density (1.6 109 cm-3) and temperature (1.3 106 K). The comparison with Chandra LETG observation of Procyon reveals that the 3s-2p line flux was significantly underestimated (by a factor of 4-5) in previous analyses. Some EUV and soft X-ray emission line ratios are -sensitive and -insensitive. Estimated electron densities from them shift downwards due to the new resonant-enhanced excitation data used in the present modelling.

KW - atomic data

KW - atomic processes

KW - plasmas

KW - stars

KW - coronae

KW - X-rays

KW - ultraviolet

KW - solar system

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DO - 10.1051/0004-6361/200811423

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SP - 943

EP - 954

JO - Astronomy and Astrophysics

T2 - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 3

ER -