Shape coexistence in Ne isotopes and hyperon impurity effect on low-lying states

Based on the beyond-mean-field Skyrme-Hartree-Fock model, we investigate the shape coexistence in Ne isotopes and the effect of Λ hyperon on the energy level structure in the nuclei. The up-to-date Skyrme-type NΛ interaction SLL4 and the NN interaction SGII are employed. Low-lying energy spectra of Ne20,22,24,26,28,30,32,34, including the low-lying states with J≤6, are predicted, discussed in detail, and found in good agreement with experimental results. The electric quadrupole transition rates are also examined. The coexistences of a ground state rotational band and a β vibrational band are revealed in Ne20,22,24. Unlike the previously discovered shrinkage effect of Λs on the ground state nuclei, it is found that the Λs may alter the excitation mode of the second band by affecting the distribution of the collective wave function, thereby causing the β vibrational band transitions to a vibrational band with equidistant energy levels.