Determination and Distorted-Wave Born-Approximation Analysis of the Neutron Polarization in theC12(He3,n)O14Reaction

Nine angular distributions of the neutron polarization produced in the ${\mathrm{C}}^{12}({\mathrm{He}}^3,n){\mathrm{O}}^{14}$ (ground-state) reaction were determined for ${\mathrm{He}}^3$ energies from 2.24 to 3.70 MeV. High polarizations were found at all energies, the extreme values being -0.87 at 2.39 MeV and 50°, and +0.72 at 3.70 MeV and 40°. Below 3.2 MeV, the neutron yield at 0° and the differential cross sections exhibit compound-nuclear effects. Above this energy, the 0° yield curve is structureless, and the cross section shows pronounced $l=0\mathrm{}$, diproton stripping patterns. Also, the three polarization distributions between 3.30 and 3.70 MeV are similar. An attempt was made to fit the 3.70-MeV (${\mathrm{He}}^3,n$) cross section and neutron polarization distributions with a distorted-wave Born-approximation (DWBA) analysis. Prior to this analysis, ${\mathrm{He}}^3$ elastic-scattering data were obtained over the region from 3.6 to 3.8 MeV, and optical-model parameters for the incident channel were extracted. Considering the possible compound-nuclear effects which were neglected in the fitting procedure, reasonable results were achieved with the DWBA code. One striking result was that the predicted polarization is insensitive to the ${\mathrm{He}}^3$ spin-orbit strength.