Interpretation of some electronic configurations in californium (Cf I). Application to opacity and hyperfine structure

A theoretical study of Cf I spectrum has been carried out, based on the relativistic Hartree–Fock (HFR) method and parametric calculations using Cowan codes and also using the orthogonal operator method. The calculations provide energies, compositions of wavefunctions and Landé factors, on one hand, for two odd excited configurations $5f^{10}7s7p$ and $5f^{9}6d7s^2$, which give rise to resonance lines by decaying to the ground configuration, and on the other hand, for three even configurations including the ground $5f^{10}7s^2$, and two interacting configurations $5f^{10}6d7s$ and $5f^{9}7s^{2}7p$. Transition probabilities have been calculated with the two parametric approaches for the strongest resonance lines, which are electric dipole transitions, and for the predicted magnetic dipole forbidden transitions within the ground configuration. The bound–bound contribution of opacity of Cf I from the transitions between the studied configurations is estimated under typical conditions of kilonovae. The orthogonal operator method has been applied to hyperfine structure calculations, and the results are compared with existing theoretical or experimental ones.