*Astron. Astrophys. Suppl. Ser.* **137**, 175-184

**M.C. Chidichimo ^{1} - V. Zeman^{2} -
J.A. Tully^{3} - K.A. Berrington^{4}**

1 - Department of Applied Mathematics, University of Waterloo,
Waterloo, Ontario N2L 3G1, Canada

2 - Mathematics Department, University of Nottingham, Nottingham NG7 2RD, UK

3 - Département Gian Domenico Cassini, Observatoire de la Côte d'Azur,
BP. 4229, 06304 Nice Cedex 4, France

4 - School of Science and Mathematics, Sheffield Hallam University,
Sheffield S1 1WB, UK

Received October 19, 1998; accepted March 9, 1999

Partial collision strengths for electron induced transitions in
the beryllium-like ion Fe XXIII are calculated using the Belfast
*R*-matrix programs (Berrington et al. 1995).
Our target has 98 fine structure states
corresponding to *n* = 2 and *n*' = 2, 3, 4. The present calculation
is carried out for electron impact energies in the range 3.15 to 350 Ry.
Below 115.185 Ry, corresponding to the highest excited state of our model ion,
we use the Breit-Pauli version of the *R*-matrix code.
For energies between 116 and 350 Ry we use the non-relativistic *LS*-coupling
version of the *R*-matrix code together with JAJOM (Saraph 1978).
When *T* exceeds about ten million degrees one needs to take account of
contributions to the thermally averaged collision strength
coming from electrons with energies in excess of 350 Ry. We discuss a way
of estimating these contributions. Values of are computed and
tabulated as functions of for transitions between the
,
, , ,
and states.
The temperature range is centred on
which, according to Arnaud & Rothenflug (1985),
is where Fe XXIII has maximum coronal abundance.

**Key words: **atomic data -- Sun: corona

- 1 Introduction
- 2 The calculation
- 3 The effect of resonances
- 4 Family portraits
- 5 Quality of results
- 6 Comparison with the work of others
- 7 Effective collision strengths
- References

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