Mass- and Charge-Distribution Studies in the Fission ofAu197by Intermediate-Energy Helium Ions

The absolute fission yields of twelve nuclides from the helium-ion-induced fission of ${\mathrm{Au}}^{197}$ have been determined radiochemically at 40.0, 37.0, and 33.5 MeV. The mass yield distributions were observed to be symmetric, and an upper limit of approximately 0.03% for an asymmetric fission mode was obtained. Independent and cumulative yield data were best correlated with the constant-charge-ratio postulate, although the charge distribution about $Z_p$ was Gaussian and similar to those observed by others in heavier-element nuclides. The width of the mass distributions was invariant over the energy range studied, and fewer neutrons appear to be emitted than had been previously reported. The total fission cross sections are in good agreement with those obtained by others using purely instrumental techniques.