Abstract
We differentiate the event-by-event n-γ multiplicity data from Cf252(sf) with respect to the energies of the emitted particles as well as their relative angles of emission. We determine that neutron emission enhances γ-ray emission around 0.7 and 1.2 MeV, but the only directional alignment was observed for Eγ≤0.7 MeV and tended to be parallel and antiparallel to neutrons emitted in the same event. The emission of γ rays at other energies was determined to be nearly isotropic. The presence of the emission and alignment enhancements is explained by positive correlations between neutron emission and quadrupole γ-ray emission along rotational bands in the de-exciting fragments. This observation corroborates the hypothesis of positive correlations between the angular momentum of a fragment and its intrinsic excitation energy. The results of this work are especially relevant in view of the recent theoretical and experimental interest in the generation of angular momentum in fission. Specifically, we have determined an alignment of the fragment's angular momenta in a direction perpendicular to the direction of motion. We interpret the lack of n-γ angular correlations for fission fragments near closed shells as a weakening of the alignment process for spherical nuclei. Lastly, we have observed that statistical γ rays are emitted isotropically, indicating that the average angular momentum removed by this radiation is small. These results, and the analysis tools presented in this work, represent a stepping stone for future analysis of n-γ emission correlations and their connection to angular momentum properties.
| Original language | English |
|---|---|
| Article number | 054609 |
| Journal | Physical Review C |
| Volume | 105 |
| Issue number | 5 |
| DOIs | |
| State | Published - May 2022 |
Funding
S.M. thanks R. C. Haight, and M. J. Devlin at LANSCE-LANL and M. J. Marcath for sharing the experimental data used in this analysis. This work was in part supported by the Office of Defense Nuclear Nonproliferation Research and Development (DNN R&D), National Nuclear Security Administration, U.S. Department of Energy. This work was funded in part by the Consortium for Monitoring, Technology, and Verification under Department of Energy National Nuclear Security Administration Award No. DE-NA0003920. The work of V.A.P. was performed under the auspices of UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The work of R.V. was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. J.R. acknowledges support from the Office of Nuclear Physics in the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
| Funders | Funder number |
|---|---|
| DNN R&D | |
| Office of Defense Nuclear Nonproliferation Research and Development | |
| U.S. Department of Energy | |
| National Nuclear Security Administration | DE-AC05-00OR22725, DE-NA0003920 |
| Nuclear Physics | DE-AC02-05CH11231 |
| Lawrence Livermore National Laboratory | DE-AC52-07NA27344 |