Effective collision strengths for electron impact excitation of C II

N. J. Wilson; K. L. Bell; C. E. Hudson

doi:doi:10.1051/0004-6361:20041855

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This article has an erratum: [erratum]

Issue		A&A Volume 432, Number 2, March III 2005


Page(s)		731 - 736
Section		Atomic, molecular and nuclear data
DOI		http://dx.doi.org/10.1051/0004-6361:20041855

A&A 432, 731-736 (2005)
DOI: 10.1051/0004-6361:20041855

Effective collision strengths for electron impact excitation of C II

N. J. Wilson, K. L. Bell and C. E. Hudson

Department of Applied Mathematics and Theoretical Physics, The Queen's University of Belfast, Belfast BT7 1NN, Northern Ireland
e-mail: c.hudson@am.qub.ac.uk

(Received 18 August 2004 / Accepted 8 November 2004 )

Abstract
We extend a previous calculation of effective collision strengths for electron impact excitation of the boron-like ion $\ion{C}{ii}$ . The earlier work was restricted to the excitation within the 2s²2p ground configuration and the sixteen 2s²2p-2s2p² fine-structure transitions whilst the present paper considers all fine-structure transitions among the levels arising from the lowest 16 LS states. The collisional cross sections are computed in the multichannel close-coupling R-matrix approximation, in which sophisticated configuration-interaction wave functions are used to represent the target states. The 16 states included have the following basis configurations: the 2s²2p ground state, four 2s2p² states, three 2p³ states, one 2s2p3s state as well as the 2s²3 $l(l=\rm s,p,d)$ and 2s²4 $l(l=\rm s,p,d,f)$ states. The 16 LS target states correspond to 30 fine-structure levels and lead to a total of 435 fine-structure transitions. In this paper we tabulate effective collision strengths, obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities, for electron temperatures in the range given by $\log_{10} T_{\rm e}$ (K) = 3.0-5.5, suitable for most astrophysical applications and laboratory plasma diagnostics. Significant differences from a previous calculation are noted and comparisons are made with some recent experimental data.

Key words: atomic processes -- line: formation -- methods: analytical

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