The character and prevalence of third minima in actinide fission barriers

Abstract

The double-humped structure of many actinide fission barriers is well established both experimentally and theoretically. There is also evidence, both experimental and theoretical, that some actinide nuclei have barriers with a third minimum, outside the second, fission-isomeric minimum. We perform a large-scale, systematic calculation of actinide fission barriers to identify which actinide nuclei exhibit third minima. We find that only a relatively few nuclei accessible to experiment exhibit third minima in their barriers, approximately nuclei with proton number $Z$ in the range $88\le Z\le 94$ and nucleon number $A$ in the range $230\le A\le 236$. We find that the third minimum is less than 1 MeV deep for light Th and U isotopes. This is consistent with some previous experimental and theoretical results, but differs from some others. We discuss possible origins of these incompatible results and what are the most realistic predictions of where third minima are observable.

References in corpus (2)

• Third minima in actinides - do they exist?
• Transmission resonance spectroscopy in the third minimum of 232Pa

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• Hartree-Fock-Bogoliubov study of quantum shell effects on the path to fission in ${}^{180}$Hg, ${}^{236}$U and ${}^{256}$Fm
• Revisiting the role of the $(n,\gamma f)$ process in the low-energy fission of ${}^{235}$U and ${}^{239}$Pu
• Ground state and fission properties of even-$A$ uranium isotopes from multidimensionally-constrained relativistic mean field model