Nav: Home

Neutron-rich nucleus shapeshifts between a rugby ball and a discus

June 23, 2017

An international team led by scientists from IPN Orsay (CNRS/Université Paris-Sud), CEA, and RIKEN (Japan) has performed the first spectroscopy of the extremely neutron-rich isotopes krypton 98 and 100. This experiment showed that there are two coexisting, competing quantum shapes at low energy in 98Kr, never before seen for neutron-rich Kr isotopes. The team also showed that these isotopes experience a gentle onset of deformation with added neutrons, in sharp contrast with neighboring isotopes of rubidium, strontium, and zirconium, which change shapes suddenly at neutron number 60. This study marks a decisive step towards an understanding of the limits of this quantum phase transition region, and was published in Physical Review Letters. How protons and neutrons are arranged in a nucleus depends directly on the force that binds them together. This nuclear interaction, still poorly understood, gives rise to sometimes sudden and surprising quantum phenomena like the complete spatial rearrangement of nucleons when passing from 59 to 60 neutrons in the zirconium (atomic number 40) and strontium (atomic number 38) isotopes. These abrupt changes illustrate the complex interplay between the collective properties of nuclear systems, like shapes, and their intrinsic microscopic degrees of freedom, such as neutron and proton numbers. Studying and understanding this interplay is essential for constraining nuclear models.

Until now, krypton isotopes had been studied up to 96Kr, which has exactly 60 neutrons and was known to be the stopping point for the shape transition. This experiment conducted at RIKEN permitted scientists, for the first time, to determine the energy of the first excited states in 98,100Kr and to evidence a progressive increase of deformation going from 60 to 62 or 64 neutrons. Beyond the somewhat slower evolution of the equilibrium shape for these nuclei, an excited state measured at low energy hints at the presence of another competing configuration. Theoretical models link the presence of these low-lying states to the coexistence of two different ellipsoidal shapes at low energy.

These results were made possible by the production of very neutron-rich nuclei at the Radioactive Isotope Beam Factory (RIBF) at the RIKEN Nishina Center for Accelerator-Based Science in Japan. Approximately 150 billion uranium 238 nuclei per second were accelerated to 70% of the speed of light and collided with a beryllium target. The fission products created during this collision were sorted in-flight by a magnetic spectrometer and sent onto a cryogenic liquid hydrogen target to synthesize the nuclei of interest via proton knockout. These knockout reactions were identified via a time projection chamber located around the thick liquid hydrogen target (100 mm), comprising a system known as MINOS. Finally, the electromagnetic de-excitation that occurs quasi-instantaneously for these exotic nuclei was detected with the DALI2 detector, which detects gamma rays emitted by nuclei using 186 scintillators. The combination of these instruments and technologies is world-unique, and essential for studying these heretofore inaccessible nuclei.


Related Neutrons Articles:

Researchers overcome the space between protons and neutrons to study heart of matter
Nuclear physicists have entered a new era for probing the strongest force in the universe at its very heart with a novel method of accessing the space between protons and neutrons in dense environments.
New neutron detector can fit in your pocket
Researchers at Northwestern University and Argonne National Laboratory have developed a new material that opens doors for a new class of neutron detectors.
Neutrons optimize high efficiency catalyst for greener approach to biofuel synthesis
Researchers led by the University of Manchester used neutron scattering at Oak Ridge National Laboratory in the development of a catalyst that converts biomass into liquid fuel with remarkably high efficiency and provides new possibilities for manufacturing renewable energy-related materials.
Scientist confirm a new 'magic number' for neutrons
An international collaboration led by scientists from the University of Hong Kong, RIKEN (Japan), and CEA (France) have used the RI Beam Factory (RIBF) at the RIKEN Nishina Center for Accelerator-base Science to show that 34 is a ''magic number'' for neutrons, meaning that atomic nuclei with 34 neutrons are more stable than would normally be expected.
Students make neutrons dance beneath UC Berkeley campus
Nuclear reactors are still the primary source for strong neutron beams to create isotopes for geologic dating, radiography and medicine, but researchers at UC Berkeley have enlisted engineering students in building a tabletop neutron source that could be nearly as effective.
Visualizing strong magnetic fields with neutrons
Researchers at the Paul Scherrer Institute PSI have developed a new method with which strong magnetic fields can be precisely measured.
Nuclear 'magic numbers' collapse beyond the doubly magic nickel 78
Scientists have demonstrated that nickel 78, a neutron-rich 'doubly magic' isotope of nickel with 28 protons and 50 neutrons, still maintains a spherical shape that allows it to be relatively stable despite the large imbalance in the number of protons and neutrons.
Through thick and thin: Neutrons track lithium ions in battery electrodes
Lithium-ion batteries are expected to have a global market value of $47 billion by 2023, but their use in heavy-duty applications such as electric vehicles is limited due to factors such as lengthy charge and discharge cycles.
'Featherweight oxygen' discovery opens window on nuclear symmetry
Researchers at Washington University in St. Louis have discovered and characterized a new form of oxygen dubbed 'featherweight oxygen' -- the lightest-ever version of the familiar chemical element oxygen, with only three neutrons to its eight protons.
Neutrons paint atomic portrait of prototypical cell signaling enzyme
Direct observations of the structure and catalytic mechanism of a prototypical kinase enzyme -- protein kinase A or PKA -- will provide researchers and drug developers with significantly enhanced abilities to understand and treat fatal diseases and neurological disorders such as cancer, diabetes, and cystic fibrosis.
More Neutrons News and Neutrons Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at