TY  - JOUR
AU  - Yokoyama, R. et al
AU  - Tain, J. L.
AU  - Algora, A.
AU  - Agramunt, J.
AU  - Domingo-Pardo, C.
AU  - Morales, A. I.
AU  - Rubio, B.
AU  - Tolosa-Delgado, A.
PY  - 2019
DA  - 2019//
TI  - Strong one-neutron emission from two-neutron unbound states in beta decays of the r-process nuclei Ga-86,Ga-87
T2  - Phys. Rev. C
JO  - Physical Review C
SP  - 031302
EP  - 6pp
VL  - 100
IS  - 3
PB  - Amer Physical Soc
AB  - beta-delayed one-neutron and two-neutron branching ratios (P-1n and P-2n) have been measured in the decay of A = 84 to 87 Ga isotopes at the Radioactive-Isotope Beam Factory (RIBF) at the RIKEN Nishina Center using a high-efficiency array of He-3 neutron counters (BRIKEN). Two-neutron emission was observed in the decay of Ga-84,Ga-85,Ga-87 for the first time and the branching ratios were measured to be P-2n = 1.6(2)%, 1.3(2)%, and 10.2(28)(stat)(5)(sys)%, respectively. One-neutron branching ratio of Ga-87 (P-1n = 81(9)(stat)(8)(sys)%) and half-life of 29(4) ms were measured for the first time. The branching ratios of Ga-86 were also measured to be P-1n = 74(2)(stat)(8)(sys)% and 16.2(9)(stat)(6)(sys)% with better precision than a previous study. The observation that P-1n > P-2n for both Ga-86,Ga-87 was unexpected and is interpreted as a signature of dominating one-neutron emission from the two-neutron unbound excited states in Ge-86,Ge-87. In order to interpret the experimental results, shell-model and Hauser-Feshbach statistical model calculations of delayed particle and gamma-ray emission probabilities were performed. This model framework reproduces the experimental results. The shell model alone predicts P-2n significantly larger than P-1n for the Ga-87 decay, and it is necessary to invoke a statistical description to successfully explain the observation that P-1n > P-2n. Our new results demonstrate the relevance and importance of a statistical description of neutron emission for the prediction of the decay properties of multineutron emitters and that it must be included in the r-process modeling.
SN  - 2469-9985
UR  - https://doi.org/10.1103/PhysRevC.100.031302
DO  - 10.1103/PhysRevC.100.031302
LA  - English
N1  - WOS:000486641000001
ID  - Yokoyama_etal2019
ER  -