On the mechanism of beta-delayed neutron emission of 44S

Standard treatments of beta delayed neutron emission rely on the compound nucleus (CN) assumption to model statistical emission of neutrons from states above the neutron separation energy populated in beta decay. Recent results [1] on the decay of 134In show discrepancies between experiment and theory for beta-n branching ratios near shell closure. To test the validity of the CN hypothesis on a broader range of isotopes, we measure beta-n decay of neutron-rich nuclei near N=28 at the FRIB Decay Station Initiator (FDSi) [2]. We combine high-resolution gamma ray and neutron spectroscopy in a high-statistics study of neutron emission from 44Cl to 43Cl following beta decay of 44S. Experimental beta-n branching ratios are compared with statistical calculations [3]. We observe discrepancies with theory at some energies and agreement at others. The results indicate a need to better understand the mechanism of beta-delayed neutron emission, incorporating structure to explain deviations from statistical models near shell closure.

[1] J. Heideman et al., Phys. Rev. C 108, 024311 (2023).

[2] I. Cox et al., Phys. Rev. Lett. 132, 152503 (2024).

[3] W. Hauser and H. Feshbach, Phys. Rev. 87, 366 (1952).