Microscopic Description of Nuclear Fission at Finite Temperature

While a predictive, microscopic theory of nuclear fission has been elusive, advances in computational techniques and in our understanding of nuclear structure are allowing us to make significant progress. Through nuclear energy density functional theory, we study the fission of thorium and uranium isotopes in detail. These nuclides have been thought to possess hyperdeformed isomers in the third minima of their potential energy surfaces, but microscopic theories tend to estimate either shallow or non- existent third minima in these nuclei. We seek an explanation in terms of neutron shell effects. We study how the fission pathways, the symmetry, and the third minima of these nuclei evolve with increasing excitation energy. We then study the fission of mercury-180, in which a recent experiment unexpectedly discovered that this nucleus fissions asymmetrically. We find that the fission of mercury-180 and mercury-198 is driven by subtleties in shell effects on the approach to scission. We finally survey fission barrier heights and spontaneous fission half-lives of several actinide nuclei, from radium to californium. For a new energy density functional, we find good agreement between our calculations and available experimental data, lending confidence to the predictions of our theory beyond experimentally measured nuclei.