α cluster structures in unbound states in ¹⁹Ne

Department of Pure and Applied Physics, Kansai University, 3-3-35 Yamatecho, Suita, Osaka 564-8680 Japan

^a e-mail: itomk@kansai-u.ac.jp

Published online: 21 June 2016

Abstract

Cluster structures in ¹⁹Ne are studied by the microscopic and macroscopic cluster models. In the microscopic calculation, the coupled-channels problem of (³He+¹⁶O) + (α+¹⁵O) is solved, and the adiabatic energy surfaces, which are the series of the energy eigenvalues as a function of the He–O distance, are investigated. In the adiabatic energy curves, the several local minima are generated in the spatial region of the small core distance, where the neutron hole inside of the He or O nucleus is strongly coupled to the residual nuclei. The energy spectra, which are constructed from the strong coupling states, nicely reproduce the the low-lying energy levels in the ¹⁹Ne nucleus. In the macroscopic approach, the α + ¹⁵O potential is evaluated from the elastic scattering of the α + ¹⁵N system, and the resonant levels of the α + ¹⁵O system are calculated under the absorbing boundary condition. The potential model predicts the existence of the resonances above the α threshold, which has a weak-coupling scheme of the α particle and one hole inside of the ¹⁶O nucleus. The extended microscopic calculations of (³He+¹⁶O) + (α+¹⁵O) + (⁵He+¹⁴O) are performed in order to see the coupling effect of the 5p-2h configuration, which corresponds to the shell model limit of the ⁵He + ¹⁴O cluster configuration. The extended calculation suggests that the ⁵He + ¹⁴O configuration plays an important role on the formation of the 3/2⁺ resonance at 0.5 MeV with respect to the α threshold.