Is there an end to the periodic table? How many protons and neutrons can fit into a nucleus? What is the heaviest element that can exist? Is there an ‘island of stability’, where superheavy elements have unique properties and long lifetimes? The quest to discover new elements not only looks towards answering these questions, but also pushes the boundaries of our understanding of atomic structure, stability, and the forces that hold matter together. Currently, there are 118 elements known, of which 90 exist naturally on Earth. Elements heavier than fermium (100 protons) are made by combining the nuclei of two lighter elements, but not just any combination works. The five heaviest known elements today were produced by combining nuclei of a special isotope of calcium (20 protons and 28 neutrons) with actinide element nuclei. Unfortunately, this method only works up to element 118 (Oganesson). To go beyond, scientists must find a new reaction mechanism.
In a paper recently accepted to Physical Review Letters, The Heavy Element Group at Berkeley Lab’s Nuclear Science Division made a significant breakthrough. Using a beam of titanium-50 (22 protons, 28 neutrons) accelerated in the 88-Inch Cyclotron, the team successfully produced two atoms of the superheavy element Livermorium (element 116) in 22 days. This experiment marks a key step towards creating element 120 which is expected to be 10-20 times harder to make than Livermorium. If successfully made, element 120 would be the heaviest known element, occupying the eighth row of the periodic table, and edging closer to the “island of stability”. Exploring elements at the extremes can provide insights into how atoms behave, test models of nuclear physics, and map out the limits of atomic nuclei.
This work was led by Jacklyn Gates and Rodney Orford of the Nuclear Science Division’s Heavy Element Group. The collaboration includes researchers from Berkeley Lab, Lund University, Argonne National Laboratory, Lawrence Livermore National Laboratory, San José State University, University of Strasbourg, University of Liverpool, Oregon State University, Texas A&M University, UC Berkeley, Oak Ridge National Laboratory, University of Manchester, ETH Zürich, and the Paul Scherrer Institute.
Figure 1: Observed decays of 290Lv and its daughters (left) compared to the known decay properties of 290Lv (right)
Figure 2: An expanded periodic table shows where researchers expect elements 119 and 120 to be categorized if they are discovered. Credit: Marilyn Sargent/Berkeley Lab