Mass Distribution in the Fission ofNp237andPu239by Intermediate-Energy Helium Ions

Cross sections have been determined for 25 representative fission products in the fission of ${\mathrm{Np}}^{237}$ by 20.0-, 25.0-, 28.4-, 32.5-, 37.5-, and 40.5-MeV helium ions and for ${\mathrm{Pu}}^{239}$ by 21.5- and 32.0-MeV helium ions. Mass distribution curves have been constructed from the data and the fission and total reaction cross sections determined. Various nuclear parameters are calculated and compared with other fission systems, and with theory.