Background: Alpha decay is a key decay mode for determining the stability and experimental identification of heavy and superheavy nuclei. Within the Wentzel–Kramers–Brillouin tunneling framework $\left(P_{\mathrm{WKB}}\right)$, the half-life depends exponentially on the effective barrier and is therefore highly sensitive to the decay energy $\left(Q_{\alpha }\right)$ and to the $\alpha$-daughter interaction. Although the dominant role of $Q_{\alpha }$ is well established, the relative importance of surface-structure effects—including the neutron-skin change ${\delta }_{n\alpha }$ between parent and daughter nuclei, the isospin asymmetry $\delta$, and the short-range repulsion described by the diffuseness parameter $a_{\mathrm{rep}}$—has not been compared within a common normalized framework. This makes it difficult to rank the mechanisms that control $\alpha$ decay in heavy and superheavy even-even nuclei.

Purpose: We quantify how the decay energy $Q_{\alpha }$ and the neutron-skin change ${\delta }_{n\alpha }$ affect the occurrence of $\alpha$ decay in even-even nuclei with $94\le Z\le 118$. By combining correlation analysis with a normalized sensitivity study of ${log}_{10}{P}_{\mathrm{WKB}}$, we compare the relative effects of $Q_{\alpha }$, ${\delta }_{n\alpha }$, $\delta$, and $a_{\mathrm{rep}}$ on the decay process.

Methods: We systematically survey even-even nuclei in the region $94\le Z\le 118$, where ${\delta }_{n\alpha }$ is computed self-consistently within two independent microscopic frameworks: the Hartree–Fock–Bogoliubov approach in the transformed harmonic-oscillator basis (HFB-THO) and the Hartree–Fock–BCS (HF-BCS) model. To compare the effects of the quantities entering the barrier penetration problem, we introduce a globally normalized linear sensitivity measure for ${log}_{10}{P}_{\mathrm{WKB}}$. For the first time, the short-range repulsive core diffuseness parameter $a_{\mathrm{rep}}$ in the double-folding (DF) potential is analyzed on the same normalized footing as $Q_{\alpha }$, ${\delta }_{n\alpha }$, and the isospin asymmetry.

Results: A systematic analysis in the region $94\le Z\le 118$ shows that the occurrence of $\alpha$ decay is strongly correlated with the behavior of ${\delta }_{n\alpha }$. Nuclei with observed $\alpha$ decay clusters within a narrow interval ${\delta }_{n\alpha }\approx 0.006–0.008\mathrm{fm}$, whereas nondecaying systems often show local deviations from this interval, even when $Q_{\alpha }$ is positive or relatively large. Strong variations of ${\delta }_{n\alpha }$ appear near deformed neutron shells ($N\approx 140\text{to}N\approx 150$) and toward the predicted near-spherical configurations around $N\approx 172$ and $N\approx 184$, where $\alpha$ decay becomes dominant. The normalized sensitivity analysis of ${log}_{10}{P}_{\mathrm{WKB}}$ shows that, beyond the leading role of $Q_{\alpha }$, the quantities $\delta$ and $a_{\mathrm{rep}}$ can make contributions of comparable size in selected nuclear regions. By contrast, local isospin-surface effects mainly provide secondary corrections because ${\delta }_{n\alpha }$ varies only within a limited range among $\alpha$-emitting nuclei. These findings show how decay energy, barrier geometry, and nuclear structure jointly affect the $\alpha$-tunneling probability.

Conclusions: The results show that $\alpha$ decay in heavy and superheavy nuclei is not controlled solely by $Q_{\alpha }$, but is also affected by surface structure and short-range interactions. The quantity ${\delta }_{n\alpha }$ is a sensitive indicator of the structural match between parent and daughter nuclei, and its deviations reflect deeper structural changes such as shell effects or shape transitions rather than acting as a direct control parameter. The relatively high sensitivity of $a_{\mathrm{rep}}$ highlights the role of short-range repulsion and Pauli blocking in shaping the inner part of the Coulomb barrier. This suggests that improved microscopic treatments of the repulsive core may be important for describing $\alpha$ decay in superheavy systems. The present framework provides a quantitative way to assess surface-structure effects across the superheavy region.

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• Alpha decay
• Nuclear reactions
• Nuclear structure & decays
• A ≥ 220