Fission Excitation Functions

Excitation functions of the reactions $\mathrm{U}(\alpha ,\mathrm{fission})$, $\mathrm{Th}(\alpha ,\mathrm{fission})$, $\mathrm{U}(d,\mathrm{fission})$, $\mathrm{Th}(d,\mathrm{fission})$ were measured by use of alpha-particles and deuterons of maximum energies of 37.6 and 18.8 Mev, respectively. This was done using a stacked-foil technique. Recoil fission fragments were collected on aluminum "catchers" and their beta-activities formed a relative measure of the number of fissions occurring during a bombardment. An absolute calibration is described. If no competing processes are assumed, comparison with theory results in effective nuclear radii of 11.0×${10}^{-13\mathrm{}}$ cm for the interaction of alpha-particles with uranium and 9.9×${10}^{-13\mathrm{}}$ cm for the interaction of deuterons with uranium.