Prescission neutron multiplicities (${\nu }_{\text{pre}}$) provide a sensitive probe of dissipation strength ($\beta$) and the timescales governing fission dynamics. We report a systematic study of neutron emission in the ${}^{28}\mathrm{Si}+{}^{232}\mathrm{Th}$ reaction forming the transactinide compound nucleus ${}^{260}\mathrm{Rf}$ over a wide excitation energy range $55\le E^{*}\le 91\mathrm{MeV}$. The extracted pre- and postscission neutron multiplicities are compared with Langevin dynamical model calculations incorporating dissipation and formation delay. It is found that the measured ${\nu }_{\text{pre}}$ are best reproduced only when both large dissipation coefficient ($\beta \approx 25\mathrm{MeV}/\hslash$) and substantial formation delays (${\tau }_{\text{form}}>100 \hslash /\mathrm{MeV}$) are included. The extracted delay time of $\approx 65$ zs for ${}^{260}\mathrm{Rf}$ is comparable to the earlier reported values for the ${}^{256,258}\mathrm{Rf}$ isotopes, pointing towards the possibility of precompound delays in the ${}^{28}\mathrm{Si}+{}^{232}\mathrm{Th}$ system. The results demonstrate the crucial role of entrance channel effects, particularly projectile-target deformation, in contributing to understand fission dynamics of heavy and superheavy nuclei. The average neutron multiplicity (${\nu }_{\text{sf}}=4.1$) is also determined for the spontaneous fission of ${}^{260}\mathrm{Rf}$ and is found to be in good agreement with the reported values for ${}^{256,258,260}\mathrm{Rf}$ isotopes and superheavy nuclei.

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• Fission
• Low & intermediate energy heavy-ion reactions
• Nuclear reactions
• A ≥ 220