Unbound states in 17C and p-sd shell-model interactions

TL;DR

This study investigates unbound states in 17C through one-neutron removal experiments, identifying resonances and comparing results with shell-model calculations, notably highlighting the effectiveness of the YSOX interaction.

Contribution

The paper provides detailed experimental data on unbound states in 17C and demonstrates that the YSOX shell-model Hamiltonian accurately describes these states and neighboring isotopes.

Findings

Resonances observed at specific energies above decay threshold.

Identification of p-shell hole states with specific spin-parities.

YSOX Hamiltonian matches experimental results well.

Abstract

Unbound states in 17C were investigated via one-neutron removal from a 18C beam at an energy of 245 MeV/nucleon on a carbon target. The energy spectrum of 17C, above the single-neutron decay threshold, was reconstructed using invariant mass spectroscopy from the measured momenta of the 16C fragment and neutron, and was found to exhibit resonances at Er=0.52(2), 0.77(2), 1.36(1), 1.91(1), 2.22(3) and 3.20(1) MeV. The resonance at Er=0.77(2) MeV [Ex=1.51(3) MeV] was provisionally assigned as the second 5/2+ state. The two resonances at Er=1.91(1) and 3.20(1) MeV [Ex=2.65(2) and 3.94(2) MeV] were identified, through comparison of the energies, cross sections and momentum distributions with shell-model and eikonal reaction calculations, as p-shell hole states with spin-parities 1/2- and 3/2-, respectively. A detailed comparison was made with the results obtained using a range of shell-model interactions. The YSOX shell-model Hamiltonian, the cross-shell part of which is based on the monopole-based universal interaction, was found to provide a very good description of the present results and those for the neighbouring odd-A carbon isotopes - in particular for the negative parity cross-shell states.