A nucleon–nucleus optical model for A ≤ 13 nuclei at 65–75 MeV projectile energy

Abstract

Small nuclei (A < 16) test the limits of optical potential theory, most recently there has been difficulty matching the helium isotopes’ analyzing powers at 71 MeV per nucleon. We provide a phenomenological optical potential that has been fit to a variety of experimental proton–nucleus and neutron–nucleus scattering data between A = 4 and A = 13 with a projectile energy between 65 and 75 MeV; the motivation being the helium isotopes. The resulting potential is dependent only on projectile isospin, neutron, and proton numbers. It fits the analyzing power of 6He satisfactorily only by including a non-traditional negative surface depth and a spin–orbit force which is significant at a distance larger than traditional models. We offer physical interpretations of our non-traditional results, suggest directions for microscopic calculations, and proffer calculations for future experiments.