Fission of Gold by Carbon Ions

Abstract

Angular distribution and kinetic-energy spectra of fragments, and cross sections for fission of gold with 68- to 124-Mev ${\mathrm{C}}^{12}$ions have been obtained by observation of the fragments in two types of detectors, gas scintillation chambers and silicon $p\ensuremath{-}n$ junctions. From the parameters used to fit the angular distributions to the theoretical curves of Halpern and Strutinski, we have obtained the average excitation energy of the fissioning nucleus at the time of fission. This quantity is approximately 25 Mev, which is nearly independent of bombarding energy, suggesting that fission is preceded by the emission of several particles from the compound nucleus. The fission cross section increases from a value of 100 mb at 68 Mev to 1.28 b at 124 Mev. Over this range of bombarding energies, the total fragment kinetic-energy release rises from 142\ifmmode\pm\else\textpm\fi{}6 to 146\ifmmode\pm\else\textpm\fi{}6 Mev. At all bombarding energies, the variation of laboratory-system kinetic energy of the fragments with laboratory-system angle indicates full momentum transfer by the bombarding particle to the fissioning system.