Study ofHe3+He3Elastic Scattering and the NucleusBe6

Abstract

Differential cross sections for ${\mathrm{He}}^{3}$ + ${\mathrm{He}}^{3}$ elastic scattering have been measured at 18 angles from 12.5 to 45\ifmmode^\circ\else\textdegree\fi{} (lab) at energies of 17.91, 20.00, 22.00, 24.00, 26.00, 28.00, and 30.00 MeV (lab). In addition, differential cross sections have been measured at intermediate energies from 19.00 to 32.00 MeV (lab) at angles of 20, 28, 36, and 45\ifmmode^\circ\else\textdegree\fi{} (lab). The relative standard deviations of the data are generally less than 2%, and there is an additional standard deviation in the cross-section scale of 3%. The measurements are compared with theoretical calculations using the resonating-group method in the one-channel approximation. A broad resonance in the $l=3$ partial wave is predicted by the theory, and such a resonance has been observed in the present experiment. Differences between theory and experiment can be qualitatively understood as being caused principally by omission in the theory of reaction channels and noncentral forces. The effect of radial distortion in resonating-group calculations for the ${\mathrm{He}}^{3}$ + ${\mathrm{He}}^{3}$ system has also been investigated in an approximate manner. It is found that the effect can be quite significant for calculations of the energies of states in ${\mathrm{Be}}^{6}$ below the ${\mathrm{He}}^{3}$ + ${\mathrm{He}}^{3}$ threshold.