Importance of resonance widths in low-energy scattering of weakly bound light-mass nuclei

Abstract

What effect do particle-emitting resonances have on the scattering cross section? What physical considerations are necessary when modelling these resonances? These questions are important when theoretically describing scattering experiments with radioactive ion beams which investigate the frontiers of the table of nuclides, far from stability. Herein, a novel method is developed that describes resonant nuclear scattering from which centroids and widths in the compound nucleus are obtained when one of the interacting bodies has particle unstable resonances. The method gives cross sections without unphysical behavior that is found if simple Lorentzian forms are used to describe resonant target states. The resultant cross sections differ significantly from those obtained when the states in the coupled channel calculations are taken to have zero width, and compound-system resonances are better matched to observed values.

Role of Target Resonances In Low-energy nucleon and α Interactions with Weakly-bound Nuclei

“…Most do not seem to contribute significantly to scattering cross sections however. Data have been obtained using a radioactive ion beam of 6 He, which, by using inverse kinematics, in Fig. 7 compare favourably with our MCAS calculations.…”

“…The Heaviside function ensures proper bound-state properties since, without it, the Green's functions are complex for E ≤ 0. More details of this method and applications are given in a recent publication [6].…”

“…Now we consider target nuclei that have particle emissive resonant states in their low-lying spectrum. Specifically we have used 8 Be and 6 He as targets in MCAS cluster model calculations. The low lying spectra of these two nuclei are shown in Fig.…”

A multi-channel model for an $ \alpha$ α plus 6He nucleus cluster

“…Full details are available in Ref. [15]. The 6 He states' properties, along with the strengths of the OPP by which the α particle orbits are hindered, are shown in Table I.…”

“…The first excited resonance state is narrow (113 keV) while the second is quite broad (12 MeV [11]). Such properties have had impact in cluster model evaluations of spectra of other compound systems [12][13][14][15].…”