Structure of Ne 20 states in resonance O 16 +α elastic scattering

Background: The nuclear structure of the cluster bands in Ne20 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 Ne20 α-cluster structure. Method: The thick target inverse kinematics (TTIK) technique was used to study O16+α resonance elastic scattering and the data were analyzed using an R-matrix approach. The Ne20 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 Ne20: 0+ level at 8.77±0.150 MeV with a width of 750-220+500 keV; 2+ level at 8.75±0.100 MeV with the width of 695±120 keV; the width of 9.48 MeV level of 65±20 keV; and we showed that the 9.19 MeV, 2+ level (if it exists) should have a width of ≤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 α-cluster levels in Ne20. The CNCIM gives a good description of the Ne20 positive-parity states up to an excitation energy of ∼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.