Configuration-interaction perturbation theory of neutral plutonium

Pu I with eight valence electrons is even more difficult for atomic calculations than Pu II, which we reported at last DAMOP, due to strong valence-valence and valence-core interactions requiring significant computation resources. We use a 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 to account for valence-electron interaction. With adjustment parameters to improve agreement between experiment and theory, we achieved quite close agreement of 300 inverse cm. We would like to report our recent CI-PT Pu I calculations of energies and other properties. In addition, we are exploring other methods and atomic codes and will provide comparison.