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

TL;DR

This study uses Regge-pole calculations to explore low-energy electron scattering from actinide atoms Cm and No, revealing novel polarization effects, shape resonances, and minima influenced by size and orbital effects, and clarifying electron affinity ambiguities.

Contribution

It introduces a new mechanism for tuning shape resonances and Ramsauer-Townsend minima via polarization interactions in actinide atoms and clarifies the interpretation of electron affinities in complex heavy systems.

Findings

Identification of polarization-induced metastable cross sections with deep R-T minima.

Observation of shape resonances near threshold in Cm and No.

Comparison showing inaccuracies in existing theoretical electron affinity calculations.

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.