The first identification of the proton halo in the excited state of¹³N

Abstract

We demonstrate that the radii of excited nuclear states can be estimated using the (3He, t) charge-exchange reaction and relying on the modified diffraction model.The radius of the 13 N excited state with an excitation energy of E*=2.37 MeV,which lies in a continuous spectrum, is determined. The radius of this state proves to be close to that of the mirror 3.09-MeV state of the 13 C nucleus, which possesses a neutron halo but lies in a discrete spectrum. Thereby, we demon- strate that the 2.37-MeV state of the 13 N nucleus has a proton halo. The analysis is based on published measurements of differential cross sections for relevant reactions.