Speaker
Description
Beta-delayed (β-n) neutron emitters are a focus of recent ISOLDE [Hei23, Xu23, Xu24], RIKEN [Yok19, Pho22, Yok23 ], and FRIB/NSCL [Cox24, Neu24] studies. The knowledge of the mechanism of β-delayed neutron emission and its consequences on the decay probabilities contribute to diverse areas of nuclear science, from nuclear reactors to astrophysical nucleosynthesis. Until recently, modeling the β-n process relied on the assumption of Bohr's hypothesis of the compound nucleus (CN) [Boh36, Boh39], in that cause decay of the excited nucleus, populated in β-decay, depends only on its spin, parity, and excitation energy and is independent of the formation process. Our recent experimental work suggested evidence of non-statistical β-n emission near doubly magic 132 Sn [Hei23]. Since then,another clear case has been found in the data [Xu24], and the search for more cases is ongoing using already collected data. These searches aim to verify the limits of the compound nucleus assumption's applicability and understand the underlying mechanism for non-statistical neutron emission. This is currently attributed to the concept of the doorway state, which is a neutron emitting with a strong mixing with the particle-hole excitations. These are populated in allowed β decay but with very small neutron emission widths. Measurements require access to high-quality beams of β-delayed neutron emitters and a sophisticated detection system, which combines neutron and gamma-ray detectors. To that end, we continue to build new types of neutron detectors. In the recent experiments at Isolde Decay Station, we implemented a recently developed neutron array NEXT [Hei19, Neu22], with interaction tracking capabilities and a new detector, based on new generation material, called an Organic Glass Scintillator (OGS) [War21].
While the analysis is still ongoing, the new results will be presented. I will also discuss some recent β-n results obtained with the FRIB Decay Station Initiator.
[Boh39] N. Bohr and J. A. Wheeler, Phys. Rev. 56, 426 (1939).
[Boh36] N. Bohr, Nature (London) 137, 344 (1936).
[Cox24] I. Cox et al. Phys. Rev. Lett. 132, 152503 (2024).
[Hei19] J. Heideman et al. Nucl. Instr. Meth. A 946 162528 (2019).
[Hei23] J. Heideman et al., Phys. Rev. C 108, 024311 (2023).
[Neu24] S. Neupane et al. Phys. Rev. C 110, 034323 (2024).
[Neu22] S. Neupane et al. Phys. Rev. C 106, 044320 (2022).
[Pho22] V. H. Phong et al. Phys. Rev. Lett. 129, 172701 (2022).
[War21] W. K. Warburton, J. S. Carlson, P. L. Feng Nucl. Instr. Meth. A 1018, 165778 (2021).
[Xu24] Z. Y. Xu et al. Phys. Rev. Lett. 133, 042501 (2024).
[Xu23] Z. Y. Xu et al. Phys. Rev. Lett. 131, 022501 (2023).
[Yok19] R. Yokoyama et al., Phys. Rev. C 100, 031302 (2019).
[Yok23] R. Yokoyama et al. Phys. Rev. C 108, 064307 (2023).
