Reactions Induced in12C by Nucleons of Energy 120-150 MeV

Abstract

Measurements are presented of the cross sections for producing individual states of the residual nuclei in the 12C (n, np)11B, 12C (p, pn)11C and 12C (p, 2p)11B reactions. Observation of the decay γ-radiation from these states provides the necessary energy resolution; the γ-radiation is observed in coincidence with protons suitably selected to reject other reactions which could produce γ-radiation. To a first approximation the results provide a measure of the parentage of the ground state of 12C; they are therefore discussed in terms of nuclear models. We find that mirror pairs of states are produced with equal cross sections in the mirror (p, pn) and (n, np) reactions, except for the states at 4.46 MeV in 11B and 4.32 MeV in 11C where the cross sections differ by a factor of 2. The strong production of these J = 5/2- states implies either that the ground state of 12C is not a pure shell-model state or that a two-stage scattering process occurs.