Structure of unbound neutron-rich $^{9}$He studied using single-neutron transfer

TL;DR

This study investigates the unbound neutron-rich isotope 9He using single-neutron transfer reactions, revealing its level structure and supporting the occurrence of parity inversion near the neutron threshold.

Contribution

It provides new experimental data on 9He’s level structure and confirms parity inversion, advancing understanding of neutron-rich helium isotopes.

Findings

Ground state of 9He is near the neutron threshold of 8He.

Evidence supports parity inversion in 9He.

Several excited states observed above neutron emission threshold.

Abstract

The 8He(d,p) reaction was studied in inverse kinematics at 15.4A MeV using the MUST2 Si-CsI array in order to shed light on the level structure of 9He. The well known 16O(d,p)17O reaction, performed here in reverse kinematics, was used as a test to validate the experimental methods. The 9He missing mass spectrum was deduced from the kinetic energies and emission angles of the recoiling protons. Several structures were observed above the neutron-emission threshold and the angular distributions were used to deduce the multipolarity of the transitions. This work confirms that the ground state of 9He is located very close to the neutron threshold of 8He and supports the occurrence of parity inversion in 9He.