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A&A Supplement series, Vol. 128, March II 1998, 581-588

Received February 12; accepted July 24, 1997

Effective collision strengths for electron impact excitation of XeIII, XeIV, XeVI and BaII, BaIV

T. Schöning - K. Butler

Institut für Astronomie und Astrophysik der Universität München, Scheinerstr. 1, D-81679 München, Germany


Effective electron excitation collision strengths have been calculated for fine-structure forbidden transitions within the 5pk (k=1, 3, 4) ground configurations of XeIII , XeIV , XeVI and the 5p5 configuration of BaIV . In addition calculations have been performed for allowed and forbidden transitions within the three lowest configurations of BaII . For astrophysical applications the data are tabulated in the range tex2html_wrap_inline1592 K. The applicability of the Breit-Pauli R-matrix technique to the computation of collision strengths for xenon and barium ions has been investigated by comparison with test calculations using the Dirac R-matrix method. Our data will be employed in quantitative analyses of highly excited nebular spectra, especially of NGC 7027 where important implications for the interpretation of collisionally excited transitions in the heavy ions are expected.

keywords: atomic data -- plasmas -- planetary nebulae: NGC 7027

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