Investigation Of ²³N In A Three-body Model With The Faddeev Equations

The nuclei close to the driplines(proton rich and neutron rich)have been explored by the radioactive nuclear beam.The properties of these nuclei are crucial for under-standing fundamental mechanism governing the stability and formation of the nuclei.These nuclei play an important role in the big bang nucleosysnthesis.Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons,primarily pro-tons and neutrons.The first nuclei were formed about three minutes after the Big Bang,through the process called Big Bang nucleosynthesis.Some nuclei,such as deuterium,tritium,helium,lithium,may have been formed at this time.In recent years,a lot of experimental and theoretical efforts have been devoted to the investigation of the the nuclei close to the the driplines.The discovery of the halo phenomenon proved that the basic concepts such as the density saturation,the shell structure and the magic number does not hold near the driplines.Especially the breaking of the neutron shell closure in neutron-rich N = 20 isotones is found.These exotic properties have attracted a lot of attention and various few-body methods have been adopted to calculate different few-body quantum systems.The equivalent two-body method,the Green’s Function Monte Carlo,and the THSR(Tohsaki-Horiuchi-Schuck-Ropke)wave function are applied to the few-body systems.Among these different approaches,the Faddeev equations were first formulated by Faddeev in 1960.They are very suitable to describe the exotic nucleus with a three-body structure,e.g.,an inert core nucleus plus two valence pro-tons(or two valence neutrons)。The Faddeev equations are consisted of three coupled Schrodinger equations.By solving these equations,we can get the properties of the nuclei.Various neutron-rich nuclei,including 6,8He,11Li,12,14Be,17B,and 22C have been investigated with the Faddeev formalism.It is also applied recently to the study of proton-rich nuclei,such as 17Ne,18Ne and 28S.In this paper,the Faddeev equations are applied to the neutron-drip-line nucleus 23N in a three-body model consisting of a 21N core and two valence neutrons.Using the Faddeev formalism with the realistic neutron-neutron potential and the neutron-core potential,the ground-state properties of 23N including its two-neutron separation energy are calculated,and agree well with the experiments.An new excited 23N state with a shallow two-neutron separation energy is also found at about 0.18 MeV.By evaluating the root-mean-square matter radii,the average distances between the two valence neutrons,and the average distances from the core to the center-of-mass of the valence-neutron pair,we show that the excited state of 23N has a distinct halo structure.Also,a large radius and a very extended spatial distribution are obtained for the weakly bounded excited state,which shows that this newly found state can be an Efimov state.