Ab initio description of the exotic unbound 7He nucleus

TL;DR

This paper introduces a novel unified ab initio approach combining bound and continuum state methods to accurately describe the unbound 7He nucleus, resolving experimental controversies about its excited states.

Contribution

It develops a new method coupling the no-core shell model with the resonating group method to study unbound nuclear states.

Findings

Accurately describes the ground-state resonance of 7He.

Predicts a broad 1/2- resonance above 2 MeV.

Addresses experimental discrepancies in excited state properties.

Abstract

The neutron rich exotic unbound 7He nucleus has been the subject of many experimental investigations. While the ground-state 3/2- resonance is well established, there is a controversy concerning the excited 1/2- resonance reported in some experiments as low-lying and narrow (E_R ~ 1 MeV, Gamma < 1 MeV) while in others as very broad and located at a higher energy. This issue cannot be addressed by ab initio theoretical calculations based on traditional bound-state methods. We introduce a new unified approach to nuclear bound and continuum states based on the coupling of the no-core shell model, a bound-state technique, with the no-core shell model/resonating group method, a nuclear scattering technique. Our calculations describe the ground-state resonance in agreement with experiment and, at the same time, predict a broad 1/2- resonance above 2 MeV.