Related Experiment Video
Updated: Oct 23, 2025
06:53
Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
Published on: July 27, 2018
8.9K
Generation of Fragment Angular Momentum in Fission
Jørgen Randrup1, Ramona Vogt2,3
1Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Physical Review Letters
|August 23, 2021
Summary
Nuclear fission fragment spins can be uncorrelated even if determined before scission, challenging previous conclusions. Shell and deformation effects explain the observed sawtooth pattern in fragment spin mass dependence.
Area of Science:
- Nuclear Physics
- Nuclear Reactions
- Quantum Mechanics
Background:
- Recent experimental data suggested nuclear fission fragment spins are uncorrelated.
- This led to the conclusion that spins are determined only after scission.
Purpose of the Study:
- To challenge the conclusion that uncorrelated spins imply post-scission determination.
- To explain the sawtooth mass dependence of average fragment spin.
Main Methods:
- Utilized the established event-by-event fission model "freya".
- Incorporated the nucleon-exchange mechanism.
- Included shell and deformation effects in fragment moments of inertia.
Main Results:
- Demonstrated that the nucleon-exchange mechanism generates largely uncorrelated fragment spins.
- Showed this occurs despite initial correlations in collective rotational modes.
- Validated that shell and deformation effects naturally produce the sawtooth spin-mass dependence.
Conclusions:
- Uncorrelated fragment spins do not necessitate post-scission determination.
- The freya model provides a valid counterexample to prior conclusions.
- The sawtooth spin-mass dependence is explained by pre-scission nuclear structure effects.
Related Concept Videos
02:50Nuclear Fission
10.8K
Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger binding energies per nucleon—that is, mass numbers and binding energies per nucleon that are closer to the “peak” of the binding energy graph near 56. Sometimes neutrons are also produced. This decomposition of a large nucleus into smaller pieces is called fission. The breaking is rather random with the formation of a large...
10.8K
02:36Nuclear Power
8.5K
Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by bombardment with neutrons has six components: nuclear fuel consisting of fissionable material, a nuclear moderator, a neutron source, control rods, reactor coolant, and a shield and containment system.
Nuclear Fuels
Nuclear fuel consists of a fissile isotope, such as uranium-235, which must be present in sufficient quantity to provide a...
Nuclear Fuels
Nuclear fuel consists of a fissile isotope, such as uranium-235, which must be present in sufficient quantity to provide a...
8.5K
01:20Mass Spectrometry: Molecular Fragmentation Overview
4.2K
The ionization of a molecule into a molecular ion inside the mass spectrometer causes instability in the molecule's structure due to the loss of an electron. This eventually leads to the fragmentation or breaking of some bonds in the molecule. The fragmentation occurs predominantly at specific bonds to yield relatively stable fragments.
One type of fragmentation pattern is the cleavage of a single bond in the molecular ion. The cleavage leads to a radical and a cation. The cleavage can...
One type of fragmentation pattern is the cleavage of a single bond in the molecular ion. The cleavage leads to a radical and a cation. The cleavage can...
4.2K
02:45Nuclear Fusion
32.5K
The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process called fusion. The principal source of energy in the sun is a net fusion reaction in which four hydrogen nuclei fuse and ultimately produce one helium nucleus and two positrons.
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
32.5K
01:10Angular Momentum: Single Particle
6.7K
Angular momentum is directed perpendicular to the plane of the rotation, and its magnitude depends on the choice of the origin. The perpendicular vector joining the linear momentum vector of an object to the origin is called the “lever arm.” If the lever arm and linear momentum are collinear, then the magnitude of the angular momentum is zero. Therefore, in this case, the object rotates about the origin such that it lies on the rim of the circumference defined by the lever arm...
6.7K
01:23Atomic Nuclei: Nuclear Relaxation Processes
793
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
793