An ab initio study of the f–f spectroscopy of americium +3

Abstract

The levels associated with the lowest F7 and D5 terms of Am+3 have been calculated using ab initio spin–orbit configuration interaction techniques. A series of configuration interaction calculations were carried out that include significant amounts of single and double excitations and with two different pseudopotentials available in the literature. Double and single excitations from the 6s, 6p, and 5f subshells are all important in the determination of the level energies. A comparison of the two examined pseudopotentials with increasing amounts of electron correlation indicates that both yield results in qualitative agreement with experiment. More importantly, though, it is estimated that both are in significant quantitative error relative to experimental results, even for very large configuration interaction calculations. The calculations were performed using the new parallel spin–orbit configuration interaction component to the COLUMBUS Program System.