Two back-to-back experiments, ${}^{28}\mathrm{Si} + {}^{178}\mathrm{Hf}$ and ${}^{28}\mathrm{Si} + {}^{186}\mathrm{W}$, were intentionally conducted to validate the role of shell closure in pre-actinides by studying neutron multiplicity in compound nucleus (CN) ${}^{206}\mathrm{Rn}$ and ${}^{214}\mathrm{Ra}$. In the first experiment [Dubey et al., Phys. Rev. C 112, L011602 (2025)], we established the influence of the neutron-shell closure. In the present work, the CN ${}^{214}\mathrm{Ra}$ was deliberately selected to investigate the dependence of the total neutron multiplicity ($M_{\mathrm{total}}$) on the proton number ($Z$), while keeping the neutron number constant at $N$ = 126 in the pre-actinide region. The objective of the study is twofold : (i) to examine the effect of proton-shell closure when moving away from $Z$ = 82, and (ii) to correlate the present results on proton-shell closure with our previous finding on neutron-shell closure. We have also used the previous reported data for $N$ = 126 isotones ${}^{210}\mathrm{Po}, {}^{212}\mathrm{Rn}$, and ${}^{213}\mathrm{Fr}$ to establish the validation of shell closure. A systematic increase in $M_{\mathrm{total}}$ with increasing $Z$ was observed from $Z$ = 82 to $Z$ = 88. Furthermore, comparison of the present results on proton-shell closure with our earlier neutron-shell closure observation, reveals that the cross correlation between neutron- and proton-shell closure shows a systematic increase in $M_{\mathrm{total}}$ as one moves away from ${}^{208}\mathrm{Pb}$, whether along isotonic or isotopic chains.

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• Low & intermediate energy heavy-ion reactions
• Nuclear reactions
• 190 ≤ A ≤ 219