Possible shape coexistence in odd-A Ne isotopes and the impurity effects of Λ hyperons

In this study, shape evolution and possible shape coexistence are explored in odd-A Ne isotopes in the framework of the multidimensionally constrained relativistic-mean-field (MDC-RMF) model. By introducing s(Lambda) and p(Lambda) hyperons, the impurity effects on the nuclear shape, energy, size, and density distribution are investigated. For the NN interaction, the PK1 parameter set is adopted, and for the Lambda N interaction, the PK1-Y1 parameter set is used. The nuclear ground state and low-lying excited states are determined by blocking the unpaired odd neutron in different orbitals around the Fermi surface. Moreover, the potential energy curves (PECs), quadrupole deformations, nuclear r.m.s. radii, binding energies, and density distributions for the core nuclei as well as the corresponding hypernuclei are analyzed. By examining the PECs, possibilities for shape coexistence in Ne-27,Ne-29 and a triple shape co-existence in Ne-31 are found. In terms of the impurity effects of Lambda hyperons, as noted for even-even Ne hypernuclear isotopes, the s(Lambda) hyperon exhibits a clear shrinkage effect, which reduces the nuclear size and results in a more spherical nuclear shape. The p(Lambda) hyperon occupying the 1/2(-)[110] orbital is prolate, which causes the nuclear shape to be more prolate, and the p(Lambda) hyperon occupying the 3/2(-)[101] orbital displays an oblate shape, which drives the nuclei to be more oblate.

Automated summary

This study explores the shape evolution and possible shape coexistence in odd-A Ne isotopes using the multidimensionally constrained relativistic-mean-field (MDC-RMF) model. The effects of s(Lambda) and p(Lambda) hyperons on the nuclear shape, energy, size, and density distribution are investigated. It is found that Ne-27, Ne-29 exhibit shape coexistence, while Ne-31 shows a triple shape coexistence. The impurity effects of Lambda hyperons result in a more spherical nuclear shape for s(Lambda) hyperon, a more prolate shape for p(Lambda) hyperon in the 1/2(-)[110] orbital, and an oblate shape for p(Lambda) hyperon in the 3/2(-)[101] orbital.