Low-energy $^3$He($\alpha$,$\alpha$)$^3$He elastic scattering and the $^3$He($\alpha$,$\gamma$)$^7$Be reaction

TL;DR

This study models low-energy helium-3 and alpha particle reactions, revealing that capturing data and elastic scattering phase shifts cannot be simultaneously explained with a simple two-body approach, highlighting limitations in current models.

Contribution

The paper demonstrates that a simple two-body model cannot simultaneously fit elastic phase shifts and capture cross sections, emphasizing the need for more complex modeling of $^3$He($ extalpha$,$ extgamma$)$^7$Be reactions.

Findings

Capture cross section dominated by direct s-wave at very low energies.

D-wave contribution increases at several MeV energies.

Model cannot simultaneously fit elastic phase shifts and capture data.

Abstract

The cross sections of the $^3$He($\alpha$,$\alpha$)$^3$He and $^3$He($\alpha$,$\gamma$)$^7$Be reactions are studied at low energies using a simple two-body model in combination with a double-folding potential. At very low energies the capture cross section is dominated by direct s-wave capture. However, at energies of several MeV the d-wave contribution increases, and the theoretical capture cross section depends sensitively on the strength of the L=2 potential. Whereas the description of the L=2 elastic phase shift requires a relatively weak potential strength, recently measured capture data can only be described with a significantly enhanced L=2 potential. A simultaneous description of the new experimental capture data and the elastic phase shifts is not possible within this model. Because of the dominating extranuclear capture, this conclusion holds in general for most theoretical models.