Description of He isotopes using the particle-particle random-phase approximation model

Abstract

The two-neutron RPA model has been used to describe helium isotopes with N (the neutron number) = 4, 6, 7, 8 in their ground and excited states. The properties of all these isotopes are given by a single system of equations so that their properties are interdependent. Since the ground states of ${}^9$He and ${}^{10}$He are still not well established, we have looked how the properties of ${}^9$He induce the properties of the other isotopes, energies and wave functions. Our results suggest an inversion of $2s$-$1p_{1/2}$ shells in ${}^9$He. The corresponding ground states of ${}^9$He and ${}^{10}$He are slightly unbound and respectively $1/2^{+}$ and $0^{+}$ states while the $1/2^{-}$ and $0^{+}$ seen in experiments appear to be excited states. With this assumption on ${}^9$He, we get not only a nice picture of ${}^{10}$He but also a very good two-neutron separation energy in ${}^8$He.

Comments: 4 pages, 2 tables, submitted to PRC