The effect of metastable level populations on the ionization fraction of Li-like ions

J.G. Doyle, H.P. Summers, P. Bryans

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Lines from Li-like ions have been known to produce theoretical intensities under-estimated compared to lines of a similar formation temperature. Here we investigate this anomalous behaviour whereby the ionization fractions are calculated using the ADAS code considering the electron density dependence of dielectronic recombination coupled with collisional ionization from metastable levels. For the lines investigated, the line contribution functions show a clear dependence with increasing electron density. For example, C IV 1548 Angstrom shows over a factor of three enhancement for N-e = 10(12) cm(-3). The increase in the higher temperature lines is lower, but are still in the range of 30 to 60 Furthermore, all the lines have their peak contribution shifted to lower temperature. Calculating the total radiative power output at an electron density of 10(11) cm(-3), we find that the difference in the transition region is 10 - 15% while above 10(6) K the difference is around 30% compared to the low density value.
LanguageEnglish
PagesL29-L32
Number of pages4
JournalAstronomy and Astrophysics
Volume430
Issue number2
DOIs
Publication statusPublished - 1 Feb 2005

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electron density
ionization
ion
ions
density dependence
recombination
augmentation
output
effect
temperature
code

Keywords

  • atmosphere
  • di-electronic recombination
  • metastable levels
  • electron density
  • line intensity
  • UV/EUV radiation

Cite this

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title = "The effect of metastable level populations on the ionization fraction of Li-like ions",
abstract = "Lines from Li-like ions have been known to produce theoretical intensities under-estimated compared to lines of a similar formation temperature. Here we investigate this anomalous behaviour whereby the ionization fractions are calculated using the ADAS code considering the electron density dependence of dielectronic recombination coupled with collisional ionization from metastable levels. For the lines investigated, the line contribution functions show a clear dependence with increasing electron density. For example, C IV 1548 Angstrom shows over a factor of three enhancement for N-e = 10(12) cm(-3). The increase in the higher temperature lines is lower, but are still in the range of 30 to 60 Furthermore, all the lines have their peak contribution shifted to lower temperature. Calculating the total radiative power output at an electron density of 10(11) cm(-3), we find that the difference in the transition region is 10 - 15{\%} while above 10(6) K the difference is around 30{\%} compared to the low density value.",
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The effect of metastable level populations on the ionization fraction of Li-like ions. / Doyle, J.G.; Summers, H.P.; Bryans, P.

In: Astronomy and Astrophysics, Vol. 430, No. 2, 01.02.2005, p. L29-L32.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The effect of metastable level populations on the ionization fraction of Li-like ions

AU - Doyle, J.G.

AU - Summers, H.P.

AU - Bryans, P.

PY - 2005/2/1

Y1 - 2005/2/1

N2 - Lines from Li-like ions have been known to produce theoretical intensities under-estimated compared to lines of a similar formation temperature. Here we investigate this anomalous behaviour whereby the ionization fractions are calculated using the ADAS code considering the electron density dependence of dielectronic recombination coupled with collisional ionization from metastable levels. For the lines investigated, the line contribution functions show a clear dependence with increasing electron density. For example, C IV 1548 Angstrom shows over a factor of three enhancement for N-e = 10(12) cm(-3). The increase in the higher temperature lines is lower, but are still in the range of 30 to 60 Furthermore, all the lines have their peak contribution shifted to lower temperature. Calculating the total radiative power output at an electron density of 10(11) cm(-3), we find that the difference in the transition region is 10 - 15% while above 10(6) K the difference is around 30% compared to the low density value.

AB - Lines from Li-like ions have been known to produce theoretical intensities under-estimated compared to lines of a similar formation temperature. Here we investigate this anomalous behaviour whereby the ionization fractions are calculated using the ADAS code considering the electron density dependence of dielectronic recombination coupled with collisional ionization from metastable levels. For the lines investigated, the line contribution functions show a clear dependence with increasing electron density. For example, C IV 1548 Angstrom shows over a factor of three enhancement for N-e = 10(12) cm(-3). The increase in the higher temperature lines is lower, but are still in the range of 30 to 60 Furthermore, all the lines have their peak contribution shifted to lower temperature. Calculating the total radiative power output at an electron density of 10(11) cm(-3), we find that the difference in the transition region is 10 - 15% while above 10(6) K the difference is around 30% compared to the low density value.

KW - atmosphere

KW - di-electronic recombination

KW - metastable levels

KW - electron density

KW - line intensity

KW - UV/EUV radiation

U2 - 10.1051/0004-6361:200400125

DO - 10.1051/0004-6361:200400125

M3 - Article

VL - 430

SP - L29-L32

JO - Astronomy and Astrophysics

T2 - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 2

ER -