Exchange Processes inn+αScattering

The features of the kernel function in the nonlocal $n+\alpha$ interaction, derived with the resonating-group method, which uses a totally antisymmetric wave function and a nucleon-nucleon potential, is studied. This kernel function is made up of three terms, corresponding to knockout, heavy-particle-pickup, and nucleon-rearrangement processes. In the medium- and high-energy regions, the knockout process contributes mainly in the forward directions, while the heavy-particle-pickup and nucleon-rearangement processes contribute mainly in the backward directions. In particular, it is found that these latter two processes are almost entirely responsible for the occurrence of large backward-angle cross sections in the $n+\alpha$ problem. An equivalent local potential between the neutron and the $\alpha$ particle is also constructed, which, in the Born approximation, yields the same results as does the resonating-group calculation. This equivalent local potential has an explicit energy dependence and a significant amount of Majorana space-exchange component. Finally, approximation methods are proposed which contain the essential features of the antisymmetization procedure and yet could be used to consider such more complicated problems as the scattering of nucleons by medium- and heavy-weight nuclei.