Alpha emission in coincidence with fission-like fragments from Cl+Ag reactions at 10 MeV/n

Energy and angular correlations between alpha particles and fission-like fragments in the reaction of³⁵Cl+Ag at 10 MeV/n have been measured. The coincident yield is dominated by two mechanisms: sequential emission from both fragments (M _α =0.137±0.014) and alpha emission from the composite system prior to scission (M _α =0.124±0.012). The observation of nuclear shadowing for sequential emission from the fragments allowed us to estimate the “lifetime” of the 218 MeV excited¹⁴³Gd composite system as (1–3)×10^?20s. It is argued that this rather long time reflects the slow evolution in shape of the composite system and might be termed “sticking time,” since statistical-model lifetimes are typically an order of magnitude shorter. Observed also are small contributions of nonequilibrium emission in the forward direction (M _α =0.005±0.001) and a component displaying the characteristics of emission from the neck (M _α =0.010±0.002).