Meaurement of spin vs. TKE of ${}^{144}$Ba produced in spontaneous fission of ${}^{252}$Cf

Abstract

We measure the average spin of ${}^{144}$Ba, a common fragment produced in ${}^{252}$Cf(sf), as a function of the total kinetic energy (TKE). We combined for the first time a twin Frisch-gridded ionization chamber with a world-class $\gamma$-ray spectrometer that was designed to measure high-multiplicity $\gamma$-ray events, Gammasphere. The chamber, loaded with a ${}^{252}$Cf(sf) source, provides a fission trigger, the TKE of the fragments, the approximate fragment masses, and the polar angle of the fission axis. Gammasphere provides the total $\gamma$-ray yield, fragment identification through the tagging of decay $\gamma$ rays, and the feeding of rotational bands in the fragments. We determine the dependence of the average spin of ${}^{144}$Ba on the fragments' TKE by correlating the fragment properties with the distribution of discrete levels that are fed. We find that the average spin only changes by about $0.5$ $\hslash$ across the TKE range of 158-203 MeV. The virtual independence of the spin on TKE suggests that spin is not solely generated through the statistical excitation of rotational modes, and more complex mechanisms are required.

arXiv commentAccepted for publication in Phys. Rev. C

References in corpus (16)

• Calculation of fission observables through event-by-event simulation
• Using excitation-energy dependent fission yields to identify key fissioning nuclei in r-process nucleosynthesis
• Fission Fragment Decay Simulations with the CGMF Code
• Primary fission fragment mass yields across the chart of nuclides
• Generation of fragment angular momentum in fission
• Fission fragments intrinsic spins and their correlations
• Angular Momentum of Fission Fragments from Microscopic Theory
• Study of angular momentum effects in fission
• Co-production of light and heavy $r$-process elements via fission deposition
• Angular momentum of fission fragments
• MeV Gamma Rays from Fission: A Distinct Signature of Actinide Production in Neutron Star Mergers
• Generation, dynamics, and correlations of the fission fragments' angular momenta
• Microscopic description of the torque acting on fission fragments
• Directional-dependence of the event-by-event neutron-$\gamma$ multiplicity correlations in ${}^{252}$Cf(sf)
• Correlations between energy and $\gamma$-ray emission in ${}^{239}\mathrm{Pu}(n,\mathrm{f})$
• Instrumentation for correlated prompt $n$-$\gamma$ emission studies in coincidence with fission fragments

Cited by in corpus (1)

• Quantum-mechanical description of angular motion of fission fragments at scission