A&A Supplement series, Vol. 129, April I 1998, 161-172
Received July 17; accepted September 12, 1997
fine structure
transition in fluorine-like ions at higher temperaturesK.A. Berrington
, H.E. Saraph
, and
J.A. Tully
Department of Applied Mathematics & Theoretical Physics,
The Queen's University of Belfast, Belfast BT7 1NN, UK 
Department of Physics & Astronomy, University College London,
Gower Street, London WC1E 6BT, UK 
Département Giovanni Domenico Cassini, Observatoire de la Côte
d'Azur, BP. 4229, 06304 Nice Cedex 4, France
The collision strength
for the fine structure transition within the ground term of 17 fluorine-like
ions from Mg IV to Ni XX is calculated using the R-matrix method.
We include target terms with n = 3 in order to take account of the
resonance structure in 
at energies above 
.
These resonances are delineated using a fine mesh of several thousand energy
points to scan the region between the first and 27th excited terms.
Results from an earlier calculation (IRON Project Paper IV) are used to cover
the region below 
. We make use of the fact that
tends to the Born limit as the collision energy
.
The effective collision strength 
is tabulated as a function of
log
, where 
is a Z-scaled temperature.
We compare results for Si+5, Fe+17 and Ni+19 with those
obtained by Mohan and co-workers. An explanation is given for the large
discrepancy in the case of 
.
keywords: atomic data -- atomic processes