https://phys.org/news/2020-03-physicists-heavy-elements.html A long-held mystery in the field of nuclear physics is why the universe is composed of the specific materials we see around us. In other words, why is it made of "this" stuff and not other stuff? Specifically of interest are the physical processes responsible for producing heavy elements—like gold, platinum and uranium—that are thought to happen during neutron star mergers and explosive stellar events. Scientists from the U.S. Department of Energy's (DOE) Argonne National Laboratory led an international nuclear physics experiment conducted at CERN, the European Organization for Nuclear Research, that utilizes novel techniques developed at Argonne to study the nature and origin of heavy elements in the universe. The study may provide critical insights into the processes that work together to create the exotic nuclei, and it will inform models of stellar events and the early universe. The nuclear physicists in the collaboration are the first to observe the neutron-shell structure of a nucleus with fewer protons than lead and more than 126 neutrons — "magic numbers" in the field of nuclear physics. more at link.... the paper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.062502 First Exploration of Neutron Shell Structure below Lead and beyond N=126 ABSTRACT: The nuclei below lead but with more than 126 neutrons are crucial to an understanding of the astrophysical r process in producing nuclei heavier than A∼190. Despite their importance, the structure and properties of these nuclei remain experimentally untested as they are difficult to produce in nuclear reactions with stable beams. In a first exploration of the shell structure of this region, neutron excitations in 207Hg have been probed using the neutron-adding (d,p) reaction in inverse kinematics. The radioactive beam of 206Hg was delivered to the new ISOLDE Solenoidal Spectrometer at an energy above the Coulomb barrier. The spectroscopy of 207Hg marks a first step in improving our understanding of the relevant structural properties of nuclei involved in a key part of the path of the r process.
