Abstract
The authors report the theoretical study of the fine-structure intervals in the 3s3p configuration of the magnesium sequence using the extended average-level version of the multi-configuration Dirac-Fock method. The 3p3d configuration was found to interact fairly strongly with the 3s3p configuration, and the inclusion of the former configuration gives results which are in good agreement with recent experiments and the semi-empirical fit of Curtis and Ramanujam (1983).