Implications of a Weakening N = 126 Shell Closure Away from Stability for r-Process Astrophysical Conditions featuring Mengke Li (UC Berkeley)

Hosted by: Aldana Grichener (University of Arizona and Observatory)

Abstract: The formation of the third r-process abundance peak near A∼195 is highly sensitive to both nuclear structure far from stability and the astrophysical conditions that produce the heaviest elements. In particular, the N = 126 shell closure plays a crucial role in shaping this peak. Experimental data hints that the shell weakens as proton number departs from Z= 82, a trend largely missed by global mass models. In this talk, I will show how this evolving shell structure influences r-process nucleosynthesis by comparing standard mass models with strong closures to modified Duflo–Zuker models that incorporate the experimentally indicated weakening, along with several sets of β-decay rates. I will also present how these nuclear inputs change the morphology of the third peak and discuss the astrophysical conditions required to reproduce the solar pattern when the shell is weakened. The results highlight how uncertainties in the N=126 region translate into constraints on r-process sites and motivate future mass measurements and improved β-decay data for nuclei near this shell closure.