Quadrupole and octupole collectivity and cluster structures in neon isotopes

Abstract

The lowest positive- and negative-parity bands of $^{20}\mathrm{Ne}$ and neutron-rich even-even Ne isotopes are investigated using a theoretical framework based on energy density functionals. Starting from a self-consistent relativistic Hartree-Bogoliubov calculation of axially symmetric and reflection-asymmetric deformation energy surfaces, the collective symmetry-conserving states are built using projection techniques and the generator coordinate method. Overall a good agreement with the experimental excitation energies and transition rates is obtained. In particular, the model provides an accurate description of the excitation spectra and transition probabilities in $^{20}\mathrm{Ne}$. The contribution of cluster configurations to the low-energy states is discussed, as well as the transitional character of the ground state. The analysis is extended to $^{22}\mathrm{Ne}$ and the shape-coexisting isotope $^{24}\mathrm{Ne}$, and to the drip-line nuclei $^{32}\mathrm{Ne}$ and $^{34}\mathrm{Ne}$. The role of valence neutrons in the formation of molecular-type bonds between clusters is discussed.