Investigation of exotic structure of the largely deformed nucleus Al-23 in the relativistic-mean-field model

摘要

A candidate for proton halo nucleus (23) Al is investigated based on the constrained calculations in the framework of the deformed relativistic mean field (RMF) model with the NL075 parameter set. It is shown by the constrained calculations that the ground state of 23 Al has a large deformation that corresponds to the prolate shape. With that large deformation, the non-constrained RMF calculation predicts that there appears an inversion between the 2s(1/2) [211] and 1d(5/2) [202] shells. The valence proton of Al-23 is weakly bound and occupies 2s(1/2) [211] and 1d(5/2) [202] with the weights of 56% and 29%, respectively. The calculated RMS radius for matter is in agreement with the experimental one. It is also predicted that the difference between the proton RMS radius and the neutron one is very large. This suggests that there exists a proton halo in (23) Al.