Multi-modal mass-asymmetric fission of 178Pt from simultaneous mass-kinetic energy fitting

The observation of mass-asymmetric fission in neutron-deficient 180Hg dramatically expanded the region of mass-asymmetric fission found across the nuclide chart, and has led to intense experimental and theoretical investigations into the fission of sub-lead nuclei. In particular, two major questions have been raised: how many fission modes are present in the fission of sub-lead nuclides, and which shells dictate these modes? Notably, investigations of the fission modes of 178Pt have led to contrasting results. To solve this disparity, new high-statistics data have been measured at the lowest excitation energy to-date using the CUBE fission spectrometer at The Australian National University. A new fitting procedure was developed to fit the high-statistics two-dimensional mass-kinetic energy distribution without external constraints. The fission of 178Pt can best be described by three fission modes: one mass-symmetric and two massasymmetric. Comparisons to previous analyses highlight the necessity of fitting the two-dimensional mass-kinetic energy distribution, rather than fitting slices of individual one-dimensional projections of the full distribution. Systematic studies of high-statistics measurements, combined with a rigorous statistical analysis offer the best chance to determine the shell effects responsible for multi-modal massasymmetric fission in this region of the nuclide chart. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license

Automated summary

The observation of mass-asymmetric fission in neutron-deficient 180Hg expanded the region of mass-asymmetric fission and stimulated research on the fission of sub-lead nuclei. The fission modes of 178Pt were investigated, revealing the presence of three modes: one mass-symmetric and two mass-asymmetric. New high-statistics data were obtained and analyzed, highlighting the importance of fitting the two-dimensional mass-kinetic energy distribution for accurate results. Systematic studies and rigorous statistical analysis are crucial to determine the shell effects responsible for multi-modal mass-asymmetric fission in this region.