Chemically characterizing superheavy elements (Z > 103) helps us understand how relativistic effects shape the chemistry of the (superheavy) members of the periodic table. As there is no evidence for their existence in nature, short-lived radioisotopes of these exotic elements must be produced one atom at a time using intense heavy-ion beams from large accelerators directed onto heavy actinide targets. The recoiling nuclear reaction products emerge with translational energies of several tens of MeV - far beyond what chemists would normally consider “useful.” But how can one perform a chemistry experiment under such unusual conditions, and what chemical information can be extracted? This talk will first introduce the basic principles of gas-phase chemistry experiments with superheavy elements. It will then highlight selected case studies, focusing on moscovium (Mc, Z = 115) and nihonium (Nh, Z = 113) as well as livermorium (Lv, Z = 116). Finally, we will explore how these fundamental experiments connect to more applied topics, including their relevance to Generation IV nuclear reactor concepts.
The formation of the third r-process abundance peak near A approximately equal to 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 Beta 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 Beta decay data for nuclei near this shell closure.
