Angular Distributions from (n, p) Nuclear Reactions

It is shown that angular distributions of high-energy proton groups from ($n, p$) reactions should evidence sharp maxima near the forward direction, which arise from neutrons with large impact parameters interacting with protons out in the "tails" of the initial nucleus. The positions of these peaks are characterized by the allowed values of orbital angular momenta $l_n$ with which the neutron can be captured to form the final state. A study of such distributions therefore may well lead to information concerning spins and parities of nuclear energy levels, as in the case of stripping reactions. For most nuclei, compound nucleus formation should contribute little to such proton groups. For light nuclei, in order that the sharp maxima stand out above the compound nucleus background, it is probably necessary that the incident neutron energy not be near a resonance of the compound nucleus.