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Unanticipated Change in Atomic Nucleus Shape Calls Established Theories into Question
In the FRIB Decay Station initiator, a beam of excited sodium-32 nuclei gets implanted, enabling the detection of isotopic decay. This work has been credited to Gary Hollenhead, Toby King, and Adam Malin from ORNL, a part of the U.S. Department of Energy.
A recent study conducted by Oak Ridge National Laboratory has uncovered an unexpected transformation in the shape of an atomic nucleus. By analyzing data from FRIB, the researchers explored the enduring excited state of sodium-32, thereby putting traditional notions about nuclear shape and energy correlations to the test.
This groundbreaking research might have unearthed a surprising alteration in an atomic nucleus’s shape, a discovery that could potentially change our comprehension of nuclear binding, the interaction between protons and neutrons, and elemental formation. Timothy Gray from the Department of Energy’s Oak Ridge National Laboratory led this study.
Gray, a nuclear physicist, explained, “In examining nuclear shapes distant from stability with radioactive beams of excited sodium-32 nuclei, we stumbled upon an unforeseen finding that leads us to question the evolution of nuclear shapes.” The journal Physical Review Letters recently published these findings.
Examining the Complexity of Nuclear Shapes
Atomic nuclei can change their shapes and energy configurations over time. Most nuclei exist as quantum objects, either spherical or deformed in shape, like basketballs or American footballs, respectively.
The relationship between shapes and energy levels is still an unresolved issue among scientists. Current nuclear structure models have difficulty extending to areas with limited experimental information.
Traditional models sometimes contradict the observed shapes of certain exotic radioactive nuclei. Those expected to be round in their most stable states have turned out to be deformed.
The Phenomenon of Quantum State Reversals
What might lead to an inversion of a quantum state?
In theory, an excited deformed state’s energy can fall below that of a spherical ground state, making the latter the higher-energy one. This unexpected reversal has been observed in some exotic nuclei when the natural neutron-to-proton ratio is distorted. However, the excited spherical states post-reversal have remained undiscovered.
There are numerous examples of nuclei with spherical ground states and deformed excited states, and vice versa. However, nuclei with both deformed ground states and spherical excited states are rare.
In-Depth Analysis of the Data
The team led by Gray used data gathered in 2022 from the first experiment at Michigan State University’s Facility for Rare Isotope Beams (FRIB) and discovered a long-lasting excited state of radioactive sodium-32. This state survived an atypical 24 microseconds – nearly a million times longer than typical nuclear excited states.
Isomers, or long-lived excited states, indicate unexpected underlying phenomena. For example, if the excited state is spherical, the difficulty in reverting to a deformed ground state could explain its extended life.
66 participants from 20 universities and national laboratories contributed to this study, with leading investigators hailing from various institutions across the country.
Experimental Setup and Configuration
The experiment conducted in 2022 utilized the extremely sensitive FRIB Decay Station initiator (FDSi) to detect rare isotope decay signatures. This apparatus’s versatile set of detectors allowed the team to study the long-lived excited state of sodium-32, delivered within the FRIB beam.
To halt FRIB’s highly energetic radioactive beam, moving at roughly half the speed of light, a special detector was positioned at the center of FDSi. Various other detectors were also employed to measure the decay process.
The analysis of gamma-ray spectra helped determine the lifespan of the excited state. This new isomer’s 24-microsecond existence marked the longest life observed among isomers with 20 to 28 neutrons decaying by gamma-ray emission.
“We have identified two models that can equally interpret the observed energies and lifetime from the experiment,” said Gray.
Looking Forward: The Search for Answers
A more powerful experiment will be required to ascertain if the excited state in sodium-32 is spherical or deformed. More powerful beam capabilities will enable an experiment to differentiate between the two scenarios.
Gray stated, “We will analyze correlations between the angles of two gamma rays emitted in a cascade. The two possibilities will present distinct angular correlations, and with enough data, we can discern a definitive pattern.”
The results of the study were published in Physical Review Letters on June 13, 2023.
The work received support from DOE’s Office of Science.
Frequently Asked Questions (FAQs) about Nuclear Structure
What does the recent Oak Ridge National Laboratory study reveal about atomic nuclei?
The study uncovers an unexpected change in the shape of the atomic nucleus, specifically in the long-lasting excited state of sodium-32. This discovery challenges conventional nuclear shape and energy correlations.
How might this discovery impact our understanding of nuclear physics?
The surprising finding could reshape our comprehension of fundamental concepts such as nuclear binding, the interaction between protons and neutrons, and the formation of elements.
Who led the study, and where was it published?
Timothy Gray, a nuclear physicist from the Department of Energy’s Oak Ridge National Laboratory, led the study. The results were published in the journal “Physical Review Letters.”
What are nuclear isomers, and why are they important in this study?
Nuclear isomers are long-lived excited states of atomic nuclei. In this study, the unusually long-lived excited state of sodium-32, observed with a lifetime of 24 microseconds, is significant as it could provide insights into the unexpected shape change.
How was the study conducted and what was the experimental setup?
The study utilized data from the Facility for Rare Isotope Beams (FRIB) at Michigan State University. The FRIB Decay Station initiator (FDSi), a system sensitive to rare isotope decay signatures, was employed. A combination of detectors helped analyze the gamma-ray emission and time of flight data.
What role do neutron-to-proton ratios play in the observed shape changes?
When the natural neutron-to-proton ratio becomes unbalanced, certain exotic nuclei experience a role reversal where deformed states become energetically favorable. This phenomenon might lead to shifts in nuclear shape, as observed in the sodium-32 nucleus.
What future experiments are planned to further investigate this phenomenon?
To determine whether the excited state in sodium-32 is spherical or deformed, a planned upgrade to FRIB will provide more beam power, enabling a more precise experiment. This experiment will examine angular correlations between emitted gamma rays to unveil the state’s shape.
How many participants were involved in the study and what institutions were represented?
The study involved 66 participants from 20 universities and national laboratories. Leading investigators hailed from institutions including Lawrence Berkeley National Laboratory, Florida State University, Mississippi State University, the University of Tennessee, Knoxville, and ORNL.
What kind of support did the study receive?
The research received support from the U.S. Department of Energy’s Office of Science.
More about Nuclear Structure
- Oak Ridge National Laboratory
- FRIB – Facility for Rare Isotope Beams
- Physical Review Letters
- Department of Energy’s Office of Science
8 comments
noice, these scientists are like using gamma-ray detectors to catch nucleus shape-shifters? That’s some epic tech.
frickin’ awesome! sci-fi meets reality when atoms do the twist! can’t wait for the next upgrd.
some grammer mistake’s here, but, um, the discovery’s pretty cool, I guess? science FTW!
hold up, so these teeny things are playing musical chairs with their shapes? Mind = Blown!
wait, so lik, they shot these nucleus thingies, and they’re like changin’ shape? ma mindz blown!
dis sci-stuff’s rad. Isomers, gamma-rays, nucleus dance moves – I’m in awe of da cool lingo!
dude, imagine if atoms were like clay, and you could just mold ’em into diff shapes. like a nucleus Picasso!
this is, like, a total paradigm shift, questioning all the stuff we thought we knew about atomic stuff. Woah!