Strong one-neutron emission from two-neutron inbound states in beta decays of $r$-process nuclei, $^{86, 87}$Ga
ORAL
Abstract
Beta-delayed one- and two-neutron branching ratios ($P_{1n}$ and $P_{2n}$) are measured in the decay of $^{86}$Ga and $^{87}$Ga at the RI-beam Factory at RIKEN Nishina Center using a high-efficiency array of $^{3}$He neutron counters (BRIKEN). Large $P_{1n}$ values are observed in $^{87,86}$Ga compared to $P_{2n}$ which was not predicted by theoretical calculations [PRL117,092502(2016), PRC67,055802(2003), PRC93,025805(2016)]. Our shell model calculation explains the observed $P_{1n} > P_{2n}$ successfully only when combined with Hauser-Feshbach statistical model [Nucl.Phys.A913,51(2013)]. This result is the first experimental demonstration that competition between multi-particle emission channels has to be considered to predict the decay properties of multi-neutron emitters which must be included in the astrophysical $r$-process modeling.
*This research was sponsored in part by the U.S. Department of Energy under Award No. DE-FG02-96ER40983 (UTK), DE-AC05-00OR22725 (ORNL), and No. DE-NA0002132. This work was also supported by JSPS KAKENHI, UK Science and Technology Facilities Council, NKFIH, Spanish Ministerio de Eonomia y Competitividad, European Commission FP7/EURATOM, NSERC of Canada, NRF in South Korea, and Polish National Science Center.
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Presenters
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Rin Yokoyama
- Univ of Tennessee, Knoxville
- Univ. of Tennessee, Knoxville