Background: The nuclear structure of the cluster bands in ${}^{20}\mathrm{Ne}$ presents a challenge for many theoretical approaches. It is especially difficult to explain the broad $0^{+}$ and $2^{+}$ states, both at around 9 MeV excitation energy. More reliable experimental data for these levels is important for proper quantitative assessment and development of theoretical methods.

Purpose: To obtain new data on the ${}^{20}\mathrm{Ne}$ $\alpha$-cluster structure.

Method: The thick target inverse kinematics (TTIK) technique was used to study ${}^{16}\mathrm{O}+\alpha$ resonance elastic scattering and the data were analyzed using an R-matrix approach. The ${}^{20}\mathrm{Ne}$ spectrum and the cluster and nucleon spectroscopic factors were calculated using the cluster-nucleon configuration interaction model (CNCIM).

Results: We determined the parameters of the broad resonances in ${}^{20}\mathrm{Ne}$: $0^{+}$ level at $8.77\pm 0.150$ MeV with a width of ${750}_{-220}^{+500}$ keV; $2^{+}$ level at $8.75\pm 0.100$ MeV with the width of $695\pm 120$ keV; the width of 9.48 MeV level of $65\pm 20$ keV; and we showed that the 9.19 MeV, $2^{+}$ level (if it exists) should have a width of $\le 10$ keV. A detailed comparison of the theoretical CNCIM predictions with the experimental data on cluster states was made.

Conclusions: Our experimental results obtained by the TTIK method generally confirm the adopted data on $\alpha$-cluster levels in ${}^{20}\mathrm{Ne}$. The CNCIM gives a good description of the ${}^{20}\mathrm{Ne}$ positive-parity states up to an excitation energy of $\sim 7$ MeV, predicting reasonably well the excitation energy of the states and their cluster and single-particle properties. At higher excitations, a qualitative disagreement with the experimentally observed structure is evident, especially for broad resonances.

• Received 14 March 2017
• Revised 5 June 2017

DOI:https://doi.org/10.1103/PhysRevC.96.014322