Effective collision strengths for electron impact excitation of Xe III, Xe IV, Xe VI and Ba II, Ba IV

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

Received: 12 February 1997
Accepted: 24 July 1997

Abstract

Effective electron excitation collision strengths have been calculated for fine-structure forbidden transitions within the 5p^k (, 3, 4) ground configurations of Xe iii, Xe iv, Xe vi and the 5p⁵ configuration of Ba iv. In addition calculations have been performed for allowed and forbidden transitions within the three lowest configurations of Ba ii. For astrophysical applications the data are tabulated in the range  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.