Exchange Effects inHe3+He4Scattering

The elastic scattering of ${\mathrm{He}}^3$ by ${\mathrm{He}}^4$ at 44.5 MeV (c.m.) is considered within the resonating-group formalism. The existence of open reaction channels is taken into account approximately by the introduction of a phenomenological local imaginary potential into the usual resonating-group formulation of the scattering problem. By choosing the shape and strength of this potential in a reasonable manner, it is found that a fairly good fit to the experimental differential cross section can be obtained in both the forward and the backward directions. From this study it is also found that the contribution to the differential cross section at backward angles comes mainly from exchange processes which are contained in the resonating-group formalism through the use of a totally antisymmetrized wave function. The real part of the phase shift is found to have a distinct odd-even feature, and from this it is shown that if one wishes to describe the experimental scattering data by using a complex local potential, then the real part of this potential must have a significant amount of Majorana space-exchange component.