Time scale of quasifission from giant dipole resonance γ-ray yield

Giant dipole resonance (GDR) γ rays were measured in coincidence with reaction fragments in 58Ni+165Ho at 368 MeV where deep inelastic scattering and quasifission dominate the reaction. The γ spectrum associated with deep inelastic scattering events is well fitted by statistical cooling of projectile and target-like fragments with close to equal initial energy sharing. The γ spectrum associated with quasifission events is well described by statistical emission from the fission fragments alone, with only weak evidence for GDR emission from the mononucleus. A 1σ limit of τ≤11x10-21 s is obtained for the mononucleus lifetime which is consistent with the lifetimes obtained from quasifission fragment angular distributions