Nuclear shell effects play a crucial role in shaping the solar $r$-process abundance pattern, while the individual contributions of shell effects in various nuclear physics ingredients, including nuclear masses, $\beta$-decay rates, and neutron-capture rates, remain insufficiently understood. We systematically investigate the influence of the $N=82$ and $N=126$ shells on the final abundances, particularly the shell effects of three nuclear physics ingredients. Our results demonstrate that removing the nuclear shell effects disrupts key features of the $r$-process abundance distribution, causing the material to become almost uniformly distributed over a mass range of roughly $30–40$ units. In addition, the $N=82$ and $N=126$ shells exhibit opposite effects on the production of heavy nuclei with $N>126$. We further find that the propagation of shell-structure changes to nuclear masses has the largest impact on the final abundances, followed by neutron-capture rates. In contrast, within the simplified diagnostic tests adopted here, shell-related discontinuities in $\beta$-decay rates at magic numbers have only a minor direct influence on the resulting abundance pattern. In addition to magic shells, relativistic mean field (RMF) models predict the presence of spurious shells at $Z=58$ and $N=92$. We find that an artificial increase of 1 MeV in nuclear binding energy at $N=92$ produces a pronounced enhancement of abundances around $A\approx 140$, potentially altering the overall abundance pattern, whereas the $Z=58$ spurious shell has only a minor effect, causing merely a small change near the $A\approx 155$ region.

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• Nuclear structure & decays
• Nucleosynthesis in explosive environments
• r process