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Issue A&A
Volume 401, Number 3, April III 2003
Page(s) 1177 - 1183
Section Celestial mechanics and astrometry
DOI http://dx.doi.org/10.1051/0004-6361:20030131



A&A 401, 1177-1183 (2003)
DOI: 10.1051/0004-6361:20030131

Atomic data from the IRON Project

LII. Electron excitation of Ni +24
M. C. Chidichimo1, N. R. Badnell2 and J. A. Tully3

1  Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
2  Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK
3  Observatoire de la Côte d'Azur, Département Gian Domenico Cassini, BP 4229, 06304 Nice Cedex 4, France

(Received 31 October 2002 / Accepted 28 January 2003 )

Abstract
This paper reports on the calculation of collision strengths for electron induced transitions in the beryllium-like ion Ni XXV whose ground state is $\rm 1s^2\,2s^2\, ^{1}S_{0}$. We make use of the R-matrix method in conjunction with the intermediate frame coupling transformation (IFCT). The target has 98 fine structure states ${\rm 1s^2}\,nl\,n'l'\,SLJ$ corresponding to n = 2 and n' = 2, 3, 4. Our calculation extends up to 440 Ry with respect to the ground state. In order to obtain reliable rate coefficients at high temperatures ( T above $2 \times 10^7$ K) we have extended our collision strengths to much higher energies by using a variety of techniques, including use of Burgess's interactive code OmeUps. The effective collision strength $\it\Upsilon$ is tabulated against ${\rm log}\,T$ for the 45 transitions linking the lowest 10 levels. We also give results for 5 transitions in the X-ray region which are needed in solar studies. The temperature range $6.3 \le \log\, T \le 8.3$ is centred on ${\rm log}\,T = 7.1$ which is where this ion has its maximum coronal abundance.


Key words: atomic data

Offprint request: M. C. Chidichimo, mchidich@math.uwaterloo.ca




© ESO 2003


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