Fission ofRa226by 11-Mev Protons

Abstract

The fission of ${\mathrm{Ra}}^{226}$ by 11-Mev protons has been studied by using radiochemical techniques. The massyield curve of fission products shows three humps: a narrow hump centered about mass 112, corresponding to a symmetric fission mode, with two humps on either side, corresponding to an asymmetric fission mode. The measured fission yields of fission fragments at the peaks of all three humps are about the same. The heavy-fragment "wing" of the asymmetric portion of the mass-yield curve is very similar in position and shape to the corresponding member of other asymmetric mass-yield curves. The light-fragment "wing" has accordingly shifted to lower mass numbers, continuing the trend observed in the asymmetric fission-yield curves of elements heavier than radium. The central, symmetric-fission hump is of the same width as the narrow, symmetric-fission curve observed for fission of bismuth by 20-Mev deuterons. The cross section for fission of ${\mathrm{Ra}}^{226}$ by 11-Mev protons is measured to be 2±1×${10}^{-27\mathrm{}}$ ${\mathrm{cm}}^2$, and drops by a factor of about 60 when the proton energy is degraded to 9 Mev.