A team of Lawrence Berkeley National Laboratory (LBNL) scientists has discovered a new form of the human-made element mendelevium, LBNL reported on June 23. The newly created isotope, mendelevium-244, is the 17th and lightest form of mendelevium, which is element 101 on the periodic table.
Details: The team used LBNL’s 88-inch cyclotron, which accelerates powerful beams of charged particles at targets to create atoms of heavier elements, to make the new isotope. A cyclotron is a type of particle accelerator that was invented by the lab’s namesake, Ernest O. Lawrence, in 1930.
Central to the isotope’s discovery was an instrument at the 88-in. cyclotron called FIONA, or For the Identification Of Nuclide A. The “A” in FIONA represents an element’s mass number, which, for the new isotope, is 244.
History: Mendelevium was first created by LBNL scientists in 1955 and is among a list of 16 elements that the lab’s scientists discovered or helped to discover.
According to LBNL, LBNL-led teams have now discovered 12 of the 17 mendelevium isotopes and have discovered a total of 640 isotopes – about one-fifth of all known isotopes. At the close of 2019 there were 3,308 known isotopes. The new isotope discovery is the first by an LBNL-led team since 2010.
They said it: “Each isotope represents a unique combination of protons and neutrons,” said Jennifer Pore, an LBNL scientist who led the study detailing the discovery of mendelevium-244. “When a new isotope is discovered, that particular combination of protons and neutrons has never been observed. Studies of these extreme combinations are critical toward our understanding of all nuclear matter.”
There’s more: In addition to discovering the new isotope, the research team’s work also provided the first direct evidence for a decay process involving an isotope of the element berkelium. The team included scientists from the University of California-Berkeley, Lawrence Livermore National Laboratory, San Jose State University, and Sweden’s Lund University.
Researchers found evidence that mendelevium-244 has two separate chains of decay, each leading to a different half-life: 0.4 second and 6 seconds, based on different energy configurations of particles in its nucleus.
In a separate measurement stemming from the same study, the researchers found the first evidence for the alpha decay process of berkelium-236, an isotope of the element berkelium, as it transforms into americium-232, a slightly lighter isotope. Berkelium was discovered in 1949 by an LBNL-led team, according to LBNL.