The neutron-to-proton $(N/Z)$ equilibration and nucleon-transfer dynamics in heavy-ion fusion reactions leading to the superheavy nucleus ${}^{297}\mathrm{Og}$ are investigated within the dinuclear system model with a dynamical potential-energy surface (DNS-DyPES model). By studying a series of reactions induced by ${}^{44–55}\mathrm{Ca}$ on Cf isotopes, the influence of entrance-channel $N/Z$ asymmetry on fusion probability and equilibration dynamics was analyzed. It is found that reactions induced by neutron-deficient and neutron-rich projectiles exhibit a potential-energy peak at the incident point, resulting in a lower fusion barrier and a higher fusion probability. Analysis of the time evolution of the mean $N/Z$ indicates that $N/Z$ equilibration occurs within approximately 0.5 zs, and the characteristic time decays exponentially with increasing potential energy at the incident point. After reaching $N/Z$ equilibration, all systems evolve along the same trajectory on the potential-energy surface, confirming that mass and charge transfer proceed along the lowest-energy path. An analysis of the projectilelike fragment distributions indicates that $N/Z$ equilibration corresponds to an early-time redistribution of fragment distribution probabilities driven by the potential energy.

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• Heavy-ion reaction mechanisms
• Low & intermediate energy heavy-ion reactions
• Nuclear reactions
• Synthesis of new superheavy elements
• A ≥ 220