Configuration-interaction perturbation theory of Pu II with adjustable parameters

Pu II with seven valence electrons is very difficult for atomic calculations due to strong valence-valence and valence-core interactions requiring significant computation resources. Configuration-interaction many-body perturbation (CI-MPBT) approach with a spherically symmetric starting potential when seven valence electrons are removed requires a very large basis sets to achieve convergence of valence-valence CI, and hence it is quite impractical. Alternatively, we explored much more proper starting potential that incorporates six 5f electrons that approximate the valence interactions and used configuration-interaction perturbation theory (CI-PT) which is much more efficient than CI-MPBT. However, CI-PT approach was developed initially for ab initio calculations. We introduced adjustment parameters to improve agreement between experiment and theory. As the result, we achieved quite close agreement of 200 inverse cm for many levels. At the meeting we will present the latest calculations of energies and g-factors for a number of Pu II levels.

The authors are grateful to Dr. Dzuba for making his CI-PT code available for this work.