It may be possible to cram more neutrons into atomic nuclei than previously thought

A new form of sodium—the element that combines with chlorine to make salt—packs a whacking 28 neutrons in its atomic nucleus, along with the 11 protons that define its chemical identity. With more than double the 13 neutrons in natural sodium, the neutron-rich isotope of the element is so extreme that few theoretical models predicted its existence. “It’s a surprise that these neutrons keep on hanging on,” says Katherine Grzywacz-Jones, a nuclear physicist at the University of Tennessee, Knoxville, who was not involved in the work. Researchers at Japan’s RIKEN Nishina Center for Accelerator-Based Science created just a handful of sodium-39 nuclei. But their mere existence challenges physicists’ understanding of nuclear structure. It also suggests that tracing the process by which exploding stars forge many elements—a goal of a major new facility in the United States—may be more difficult than thought. Three years ago, an experiment with the RIKEN center’s particle accelerator, a superconducting cyclotron called the Radioactive Isotope Beam Factory , produced a tantalizing hint of a single sodium-39 nucleus. “Therefore, we repeated the experiment with much higher beam intensity and a longer beam time,” says Toshiyuki Kubo, a RIKEN nuclear physicist. Kubo’s 26-member team shot a beam of calcium-48 nuclei through a beryllium target to shred them and funneled the fragments through a snaking chain of magnets called BigRIPS. Rese...
Source: ScienceNOW - Category: Science Source Type: news