Beta-delayed neutron emission in the deformed nucleus ⁴⁴S

The decay of N=28 ⁴⁴S was studied in the FRIB Decay Station Initiator [1] experiment e21062b. Analysis of the neutron spectrum from the ⁴⁴Cl to ⁴³Cl neutron emission, following beta decay of ⁴⁴S, revealed unexpected results. Comparing intensities of neutron peaks populating the ground and low-lying states of ⁴³Cl, we observed much higher ground-state population than predicted by Hauser-Feshbach statistical model calculations [2]. The ground state of ⁴⁴S is believed to be moderately deformed (e.g., [3,4], among others), and the neutron-unbound states in ⁴⁴Cl populated in beta decay may be similarly deformed. We present an interpretation of the discrepancy between experiment and statistical theory as the result of transitions between deformed states in ⁴⁴S, ⁴⁴Cl, and ⁴³Cl.

[1] https://fds.ornl.gov/initiator/

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

[3] C. Force et al., Phys. Rev. Lett. 105, 102501 (2010)

[4] P. Möller et al., Atomic Data and Nuclear Tables 109-110, 1-204 (2016)