Evidence of quasifission in the 16O+238U reaction at sub-barrier energies

Mass distribution of fission fragments and neutron multiplicity in the O-16 + U-238 reaction were measured at near-and below-barrier energies. A sudden change in the fragment mass width, observed in the present measurement, confirmed the transition to quasifission at below-barrier energies; the same was indicated earlier from the study of fission fragment angular anisotropy. However, the present measurement of prescission neutron multiplicity as well as the earlier measurement of evaporation residue yield did not indicate any significant departure from the respective statistical model predictions throughout the energy range. It is argued that the first two probes are more sensitive for highly asymmetric systems, whereas all probes would be useful and complimentary to each other for study of quasifission in more symmetric systems, where quasifission is more dominant.