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Content Provider | World Health Organization (WHO)-Global Index Medicus |
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Author | Bell, K. L. Aller, L. H. Crawford, F. L. Keenan, F. P. Ramsbottom, C. A. Hyung, S. |
Description | Author Affiliation: Keenan FP ( Department of Pure and Applied Physics, The Queen's University of Belfast, Belfast BT7 1NN, Northern Ireland.); |
Abstract | Electron impact excitation rates in Cl III, recently determined with the R-matrix code, are used to calculate electron temperature (T(e)) and density (N(e)) emission line ratios involving both the nebular (5517.7, 5537.9 A) and auroral (8433.9, 8480.9, 8500.0 A) transitions. A comparison of these results with observational data for a sample of planetary nebulae, obtained with the Hamilton Echelle Spectrograph on the 3-m Shane Telescope, reveals that the R(1) = I(5518 A)/I(5538 A) intensity ratio provides estimates of N(e) in excellent agreement with the values derived from other line ratios in the echelle spectra. This agreement indicates that R(1) is a reliable density diagnostic for planetary nebulae, and it also provides observational support for the accuracy of the atomic data adopted in the line ratio calculations. However the [Cl iii] 8433.9 A line is found to be frequently blended with a weak telluric emission feature, although in those instances when the [Cl iii] intensity may be reliably measured, it provides accurate determinations of T(e) when ratioed against the sum of the 5518 and 5538 A line fluxes. Similarly, the 8500.0 A line, previously believed to be free of contamination by the Earth's atmosphere, is also shown to be generally blended with a weak telluric emission feature. The [Cl iii] transition at 8480.9 A is found to be blended with the He i 8480.7 A line, except in planetary nebulae that show a relatively weak He i spectrum, where it also provides reliable estimates of T(e) when ratioed against the nebular lines. Finally, the diagnostic potential of the near-UV [Cl iii] lines at 3344 and 3354 A is briefly discussed. |
ISSN | 00278424 |
e-ISSN | 10916490 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Issue Number | 9 |
Volume Number | 97 |
Language | English |
Publisher | National Academy of Sciences |
Publisher Date | 2000-05-01 |
Publisher Place | United States |
Access Restriction | Open |
Subject Keyword | Planets Astronomy Electrons Models, Theoretical Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Multidisciplinary |
Content Type | Text |
Resource Type | Article |
Subject | Multidisciplinary |
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