Measuring spin-energy correlations in fission with Gammasphere*

We analyze an experiment performed at Argonne National Laboratory, with the intention of expanding upon a recent experimental analysis [J. Wilson et al., Nature 590, 566 (2021)] that confirmed the existence of the spin sawtooth in nuclear fission. We combined a twin Frisch-gridded ionization chamber with Gammasphere, a world-class gamma-ray spectrometer which was designed to measure high-multiplicity gamma-ray events. The chamber, loaded with a ²⁵²Cf(sf) source, provides a fission trigger, the total kinetic energy (TKE) of the fragments, and the approximate fragment masses. 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 will determine how the spin sawtooth varies with the fragments’ TKE by correlating the fragment properties with the distribution of discrete levels that are fed. This approach allows us to explore spin-energy correlations in fission in a nearly model-independent way.