The Fission of Thorium with Alpha-Particles

The fission distribution of fission of thorium with alpha-particles of average energy 37.5 Mev has been measured by the chemical method. The distribution found shows that the characteristic dip in the fission yield mass spectrum has been raised to within a factor of two of the peaks compared to a factor of 600 in slow neutron fission of ${\mathrm{U}}^{235}$. The raise in the dip has caused a corresponding lowering in fission yield of these elements at the peaks. The cross section for fission of thorium with 37.5-Mev alphas was found to be about 0.6 barn, and the threshold for fission was found to be 23 to 24 Mev.