THE ROLE OF THE 5P(5)5D CONFIGURATION AND SPIN-ORBIT-COUPLING IN THE ELECTRON-IMPACT EXCITATION OF THE LOWEST-LYING J=0 AND J=2 LEVELS OF XENON AND KRYPTON

Calculations of electron-impact differential cross sections (DCSs) for heavy rare gases have traditionally employed a single [np(5)(n + 1)s) ] configuration to describe the lowest-lying excited levels. Such calc ulations have been applied to systems up through xenon (n = 5) with th e assumption that additional configurations would give a negligible co ntribution to the DCS. While this assumption is certainly valid for ne on and argon, Khakoo et al recently demonstrated the importance of inc luding the 5p(5)5d configuration when calculating the DCSs of the lowe st-lying J = 0 and J = 2 levels of xenon. In particular, their calcula ted ratios of these two DCSs agree better with experiment and exhibit a more radical departure from the expected 5:1 statistical value than predicted by earlier theoretical investigations. In this paper we show that the 5p(5)5d configuration in conjunction with the spin-orbit cou pling effect is responsible for the different behaviour in the cross s ections of the J = 0 and J = 2 levels. A similar, brief analysis is ap plied to the pair of lowest-lying J = 1 levels of xenon. The effect of the 4p(5)4d configuration on DCS calculations of krypton is also expl ored.