Weakly-bound rare isotopes with a coupled-channel approach that includes resonant levels

TL;DR

This paper investigates how low-excitation resonances in unstable nuclei affect scattering cross sections using a coupled-channel approach, addressing unphysical resonance tails near thresholds by modifying resonance shapes.

Contribution

It introduces a method to incorporate particle-emitting resonances in scattering calculations and corrects unphysical resonance tails near thresholds within a coupled-channel framework.

Findings

Resonant states significantly influence scattering cross sections.

Modified resonance shapes improve physical accuracy near thresholds.

The approach successfully models unstable nuclei like 8Be.

Abstract

The question of how the scattering cross section changes when the spectra of the colliding nuclei have low-excitation particle-emitting resonances is explored using a multi-channel algebraic scattering (MCAS) method. As a test case, the light-mass nuclear target 8Be, being particle-unstable, has been considered. Nucleon-nucleus scattering cross sections, as well as the spectra of the compound nuclei formed, have been determined from calculations that do, and do not, consider particle emission widths of the target nuclear states. The resonant character of the unstable excited states introduces a problem because the low-energy tails of these resonances can intrude into the sub-threshold, bound-state region. This unphysical behaviour needs to be corrected by modifying, in an energy-dependent way, the shape of the target resonances from the usual Lorentzian one. The resonance function must smoothly reach zero at the elastic threshold. Ways of achieving this condition are explored in this paper.