Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session F10: Nuclear Structure IV
9:00 AM–11:15 AM,
Thursday, November 30, 2023
Hilton Waikoloa Village
Room: Kohala 3
Chair: Krzysztof Piotr Rykaczewski, Oak Ridge National Lab
Abstract: F10.00009 : Study of the β-delayed multi-neutron emission process through γ-neutron spectroscopy of Gallium Isotopes.*
11:00 AM–11:15 AM
Presenter:
Rin Yokoyama
(Center for Nuclear Study, the University of Tokyo)
Authors:
Rin Yokoyama
(Center for Nuclear Study, the University of Tokyo)
Robert Grzywacz
(University of Tennessee)
Bertis C Rasco
(Oak Ridge National Laboratory)
Krzysztof Piotr P Rykaczewski
(ORNL)
Iris Dillmann
(TRIUMF)
Jose-Louis Tain
(IFIC, CSIC-Universitat de Valencia)
Shunji Nishimura
(RIKEN)
Collaboration:
BRIKEN collaboration
Beta-delayed neutron emission occurs in neutron-rich nuclei where the decay energy window is large enough to populate states above the neutron separation energy in the daughter nucleus. Understanding the neutron emission process is crucial since one, or even multiple, neutron emissions serve as the dominant decay modes for the neutron-rich nuclei along the r-process path. A comprehensive β-delayed γ-neutron spectroscopy study on the decay of gallium isotopes A = 84 to 87 was conducted at the RIKEN Nishina Center's RI-beam Factory. The isotopes were examined using a high-efficiency array of 3He neutron counters (BRIKEN) and two clover-type HPGe detectors, enabling β-γ-2n coincidence measurements of the excited states of two-neutron daughter nuclei. Experimental results demonstrated that both neutron and γ branching ratios, as well as P1n and P2n ratios, are sensitive to the nuclear level densities of 1n daughter nuclei and the ground-state spin of the parent nucleus. Hauser-Feshbach statistical model calculations were optimized using experimental and shell-model levels in the daughter nuclei, thereby improving the reproduction of the P2n/P1n ratio. Given that neutron emissions significantly influence the final abundance pattern of r-process nucleosynthesis, these results underscore the importance of understanding level density and having detailed comprehension of the decay scheme, which includes neutron spectroscopy data for multi-neutron emitters.
*This research was sponsored in part by the Office of Nuclear Physics, U.S. Department of Energy under Award No. DE-FG02-96ER40983 (UTK) and DE-AC05-00OR22725 (ORNL)
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