The collision strength of the [Ne V] infrared fine-structure lines
P.A.M. van Hoof, D.A. Beintema, D.A. Verner, G.J. Ferland
published in: A&A 354, L41 (2000)
The calculation of accurate collision strengths for atomic transitions
has been a long standing problem in quantitative spectroscopy. Most
modern calculations are based on the R-matrix method and problems
pertaining to the use of this method have led to a discussion of the
accuracy of these results. More in particular, based on an analysis of
the spectra of NGC 3918 and NGC 6302, Clegg et al. (1987)
and Oliva et al. (1996) have questioned R-matrix calculations for the
infrared [Ne V] fine-structure transitions. Using improved flux
measurements for the [Ne V] lines, we show that the conclusion that
these collision strengths would be too high, is not correct. The
discrepancies found by Clegg et al. (1987) can be explained by the
inaccuracy of the [Ne V] 342.6 nm flux they adopted. The
discrepancies found by Oliva et al. (1996) can be explained by the
inaccuracy of the LRS flux for the [Ne V] 14.32 µm line. Based
on the data presented in this paper there is no reason to assume
that there are any problems with the R-matrix calculations for
Ne4+ of Lennon & Burke (1994). We show that the data are
accurate at the 30 % level or better. This confirms the validity
of the close coupling method.
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Peter van Hoof
Royal Observatory of Belgium
Ringlaan 3
1180 Brussel
Belgium
email: p DOT vanhoof AT oma DOT be
