Pre-scission neutron multiplicities are measured for ${}^{12}\mathrm{C}\hspace{0.5em}+\hspace{0.5em}{}^{204}\mathrm{Pb}$ and ${}^{19}\mathrm{F}\hspace{0.5em}+\hspace{0.5em}{}^{197}\mathrm{Au}$ reactions at laboratory energies of 75–95 MeV for the ${}^{12}\mathrm{C}$ beam and 98–118 MeV for the ${}^{19}\mathrm{F}$ beam. The chosen projectile-target combinations in the present study lie on either side of the Businaro-Gallone mass asymmetry (${\alpha }_{\mathrm{BG}}$) and populate the ${}^{216}\mathrm{Ra}$ compound nucleus. The dissipation strength is deduced after comparing the experimentally measured neutron yield with the statistical model predictions which contains the nuclear viscosity as a free parameter. Present results demonstrate the combined effects of entrance channel mass asymmetry and the dissipative property of nuclear matter on the pre-scission neutron multiplicity in fusion-fission reactions.

• Received 13 June 2008

DOI:https://doi.org/10.1103/PhysRevC.78.024609