Interaction of Neutrons withHe3

Spectra of the $n$+${\mathrm{He}}^3$ reactions were obtained for monoenergetic neutron fluxes of 0.95, 2.67, 5.00, 8.07, and 17.5 Mev using a ${\mathrm{He}}^3$-filled proportional counter. Analysis of these spectra yielded the ratios to the total cross section of the total elastic, the ${\mathrm{He}}^3(n, p){\mathrm{H}}^3$, and the ${\mathrm{He}}^3(n, d)\mathrm{D}$ reaction cross sections. Absolute cross sections were obtained by normalization to the known total cross section. Differential elastic-scattering cross sections for neutrons on ${\mathrm{He}}^3$ were obtained through the relationship between the scattering angle of the neutron and the observed energy of the ${\mathrm{He}}^3$ recoil in the counter filling. These angular distributions are compared with the theoretical angular distributions as calculated by Bransden, Robertson, and Swan. The present experiment was intended to discriminate between their assumed two special cases for the potential interaction, the symmetrical exchange force and the Serber exchange force. The experimental results favor the Serber exchange force. This experiment also was intended to make possible the analysis of more complex neutron spectra by providing knowledge of $n$+${\mathrm{He}}^3$ reaction cross sections and the spectra obtained when only monoenergetic neutrons are present. A comparison is made of the results of this experiment with cross sections calculated from inverse reactions and direct measurements of other investigators, where such data are available.