Proton and $\alpha$-particle emission spectra have been measured in ${}^4\mathrm{He}+{}^{58}\mathrm{Ni}$ and ${}^4\mathrm{He}+{}^{64}\mathrm{Ni}$ reactions at energies $\gtrsim 10$ MeV/nucleon to understand the complex interplay between the equilibrium and pre-equilibrium (PE) emission processes and effect of $N/Z$ asymmetry on them. Theoretical analyses of the experimental spectra were performed using the $\mathrm{TALYS}$ code, including contributions from both equilibrium or compound nuclear (CN), and PE components. While the $\alpha$-particle spectra aligned well with default $\mathrm{TALYS}$ predictions, the proton spectra showed significant deviations due to an over-prediction of the PE component. The relative contributions of CN and PE components were extracted from the energy spectra and compared for the two systems at different angles. The analyses showed a significantly higher PE fraction in the ${}^4\mathrm{He}+{}^{64}\mathrm{Ni}$ reaction compared to ${}^4\mathrm{He}+{}^{58}\mathrm{Ni}$, suggesting a link between the $N/Z$ asymmetry and PE emission. The present study provides crucial information in refining available theoretical models and offers key insights into the underlying reaction mechanisms.

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• Nuclear reactions
• Thermal & statistical models
• 59 ≤ A ≤ 89