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A&A Supplement series, Vol. 129, April I 1998, 161-172

Received July 17; accepted September 12, 1997

Atomic data from the IRON Project

XXVIII. Electron excitation of the tex2html_wrap_inline2120 fine structure transition in fluorine-like ions at higher temperatures

K.A. Berringtontex2html_wrap2166, H.E. Saraphtex2html_wrap2168, and J.A. Tullytex2html_wrap2170

tex2html_wrap2172  Department of Applied Mathematics & Theoretical Physics, The Queen's University of Belfast, Belfast BT7 1NN, UK
tex2html_wrap2174  Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK
tex2html_wrap2176  Département Giovanni Domenico Cassini, Observatoire de la Côte d'Azur, BP. 4229, 06304 Nice Cedex 4, France


The collision strength tex2html_wrap_inline2122 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 tex2html_wrap_inline2128 at energies above tex2html_wrap_inline2130. 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 tex2html_wrap_inline2132. We make use of the fact that tex2html_wrap_inline2128 tends to the Born limit as the collision energy tex2html_wrap_inline2136. The effective collision strength tex2html_wrap_inline2138 is tabulated as a function of logtex2html_wrap_inline2140, where tex2html_wrap_inline2142 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 tex2html_wrap_inline2152.

keywords: atomic data -- atomic processes

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