New Manifestations In Low-energy Electron Scattering From The Large Actinide Atoms Cm and No

Abstract

The Regge-pole calculated low-energy electron elastic total cross sections (TCSs) for Cm and No, characterized generally by negative-ion formation, shape resonances and Ramsauer-Townsend(R-T) minima, exhibit atomic and fullerene molecular behavior near threshold. Also, a polarization-induced metastable cross section with a deep R-T minimum near threshold is identified in the Cm TCSs, which flips over to a shape resonance appearing very close to threshold in the TCSs for No. We attribute these novel manifestations to size effects and orbital collapse impacting significantly the polarization interaction. This provides a new mechanism of tuning a shape resonance and R-T minimum through the polarization interaction. The comparison between the Regge-pole calculated ground, metastable and excited states anionic binding energies(BEs) with the existing theoretical electron affinities(EAs) demonstrates that those calculations tend to obtain metastable and/or excited states BEs and equate them incorrectly with the EAs, leading to ambiguous and unreliable electron affinity determination. A definitive and unambiguous meaning of the EA of complex heavy systems is recommended.