An international team of researchers, spearheaded by Berkeley Lab‘s Heavy Element Group, has achieved a monumental feat- the discovery of the superheavy element 116 (livermorium) using a beam of titanium-50. This breakthrough not only marks a significant step towards creating the heaviest element yet, 120, but also opens up a world of possibilities in the field of nuclear physics and chemistry.
Researchers created two atoms of element 116, livermorium, using the 88-inch Cyclotron. Even though this process is rare, researchers can realistically look for a reaction that produces an element 120 atoms over several years.
Researchers say it will take about ten times longer to make 120 than 116. Even though it is challenging, it appears feasible now.
If researchers succeed, element 120 would be the heaviest atom ever made and be in the eighth row of the periodic table. It would be part of the “island of stability,” a theorized group of superheavy elements with unique properties.
So far, superheavy elements break apart immediately, but the correct blend of protons and neutrons could make a more stable and durable nucleus. This could make it easier for scientists to study.
Making superheavy elements
Making superheavy elements is simple in theory but practically- very difficult. Also, there are limitations on what elements can reasonably be turned into a particle beam or target.
Researchers chose specific isotopes for their experiments. They needed a beam of atoms with 22 protons: titanium, which is not commonly used to make superheavy elements.
The team meticulously planned and executed their experiments, verifying if they could produce a sufficiently intense beam of the isotope titanium-50 over weeks and use it to create element 116, the heaviest element ever made at Berkeley Lab.
Jennifer Pore, a scientist in Berkeley Lab’s Heavy Element Group, said, “It was an important first step to try to make something a little bit easier than a new element to see how going from a calcium beam to a titanium beam changes the rate at which we produce these elements.”
“When we’re trying to make these scarce elements, we are standing at the absolute edge of human knowledge and understanding, and there is no guarantee that physics will work the way we expect. Creating element 116 with titanium validates that this production method works and we can now plan our hunt for element 120.”
It is extremely challenging to create an intense beam of titanium isotopes. It starts with a particular hunk of titanium-50, a rare isotope of titanium. This piece is heated in an oven to nearly 3000 degrees Fahrenheit until it vaporizes.
This process occurs in an ion source called VENUS, a complex superconducting magnet that acts like a bottle confining a plasma. In this plasma, free electrons gain energy from microwaves and remove 12 of titanium’s 22 electrons. The charged titanium can then be controlled by magnets and sped up in the 88-inch Cyclotron.
Once a rare superheavy element forms, the magnets in the Berkeley Gas-filled Separator (BGS) separate it from the rest of the particle debris and send it to a sensitive silicon detector known as SHREC: the Super Heavy RECoil detector. SHREC captures energy, location, time, and information, helping researchers identify it as it breaks down into lighter particles.
Jacklyn Gates, a nuclear scientist at Berkeley Lab leading the effort, said, “We’re very confident that we’re seeing element 116 and its daughter particles. There’s about a 1 in 1 trillion chance that it’s a statistical fluke.”
Researchers still need to complete work before they attempt to make element 120. Experts at the 88-inch Cyclotron continue to prepare the machine for a target made of californium-249, and partners at Oak Ridge National Laboratory will need to craft about 45 milligrams of californium into the target.
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 collaborated on this work.
The result was presented at the Nuclear Structure 2024 conference; the science paper will be posted on the online repository arXiv and submitted to the journal Physical Review Letters.