Rigorous probing of the electronic structure of Berkelium and Californium actinide atoms

Abstract A recent experiment identified a weak spin-orbit-coupling in atomic Bk while a jj coupling scheme described atomic Cf. It concluded that these observations strengthen Cf as a transitional element in the actinide series. This paper uses Ramsauer-Townsend (R-T) minima and shape resonances (SRs) from low-energy electron elastic total cross sections (TCSs) calculated using the rigorous Regge pole method as novel confirmation of the observation. Regge pole-calculated TCSs for Bk and Cf atoms are characterized generally by ground, metastable and excited states negative-ion formation, R-T minima and SRs. Additionally, a polarization-induced metastable TCS with a deep R-T minimum near threshold characterizes the Bk TCSs, which flips over to a well pronounced SR appearing very close to threshold in the Cf TCSs. This demonstrates the sensitivity of R-T minima and SRs to the electronic structure of these atoms, thereby permitting their first time ever use as novel and rigorous validation of the experimental observation. .