Rapid energy equilibration and emission of H and He in the reaction of 340-MeVAr40withAu197

Energy and angular distributions have been measured for H and He both in singles and in coincidence with a heavy fragment. Large cross sections have been observed for both a low-temperature component at backward angles and a high-temperature component at forward angles. Both the preequilibrium and evaporationlike components are apparently emitted prior to scission, predominantly in coincidence with fragments of $Z>\mathrm{}27\mathrm{}$. The angular anisotropy and out-of-plane correlation for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are not consistent with emission from the composite systems of highest spin ($\approx 190\hslash$) but are consistent with emission from the ${}_{}{}^{237}{}_{}{}^{}\mathrm{Bk}$ composite with average spin $\approx 70\hslash$. Extensive energy sharing and H/He emission occur in many reactions so rapidly as to precede fission which is heavily favored by energetic and phase space considerations.