First determination of $\beta$-delayed multiple neutron emission beyond A = 100 through direct neutron measurement: The P${}_{2n}$ value of ${}^{136}$Sb

Abstract

Background: $\beta$-delayed multiple neutron emission has been observed for some nuclei with A$\le$100, with ${}^{100}$Rb being the heaviest $\beta$2n emitter measured to date. So far, only 25 P${}_{2n}$ values have been determined for the $\sim$300 nuclei that may decay in this way. Accordingly, it is of interest to measure P${}_{2n}$ values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such measurement for nuclei with A$>$100 to test the predictions of theoretical models and simulation tools for the decays of heavy nuclei in the region of very neutron-rich nuclei. In addition, the decay properties of these nuclei are fundamental for the understanding of astrophysical nucleosynthesis processes such as the $r$-process, and safety inputs for nuclear reactors. Purpose: To determine for the first time the two neutron branching ratio, P${}_{2n}$ value, for ${}^{136}$Sb through a direct neutron measurement, and to provide precise P${}_{1n}$ values for ${}^{136}$Sb and ${}^{136}$Te. Method: Pure beams were provided by the JYFLTRAP at the IGISOL facility of the University of Jyväskylä, Finland. The purified ions were implanted into a moving tape at the end of the beam line. The detection setup consisted of a plastic scintillator placed right behind the implantation point, and the BELEN detector, based on neutron counters embedded in a polyethylene matrix. The analysis was based on the study of the $\beta$- and neutron- growth-and-decay curves and the $\beta$-one-neutron and $\beta$-two-neutron time correlations. Results: The P${}_{2n}$ value of ${}^{136}$Sb was found to be 0.14(3)\% and the measured P${}_{1n}$ values for ${}^{136}$Sb and ${}^{136}$Te were found to be 32.2(15)\% and 1.47(6)\%, respectively. The measured P${}_{2n}$ value is a factor 44 smaller than predicted by the FRDM+QRPA model used for $r$-process calculations.

arXiv comment11 pages, 10 figures

References in corpus (10)

• The impact of individual nuclear properties on $r$-process nucleosynthesis
• Large scale evaluation of beta-decay rates of r-process nuclei with the inclusion of first-forbidden transitions
• Dynamical r-process studies within the neutrino-driven wind scenario and its sensitivity to the nuclear physics input
• A sextupole ion beam guide to improve the efficiency and beam quality at IGISOL
• Precision Mass Measurements beyond ${}^{132}$Sn: Anomalous behaviour of odd-even staggering of binding energies
• Neutron-gamma competition for $\beta$-delayed neutron emission
• First measurement of several $\beta$-delayed neutron emitting isotopes beyond N=126
• $\beta$-decay half-lives and $\beta$-delayed neutron emission probabilities for several isotopes of Au, Hg, Tl, Pb and Bi, beyond N=126
• Nuclear structure of 140Te with N = 88: Structural symmetry and asymmetry in Te isotopes with respect to the double-shell closure Z = 50 and N = 82
• Sensitivity studies for r-process nucleosynthesis in three astrophysical scenarios

Cited by in corpus (5)

• Beta-decay studies for applied and basic nuclear physics
• Neutron flux and spectrum in the Dresden Felsenkeller underground facility studied by moderated ${}^3$He counters
• First $\beta$-decay spectroscopy of ${}^{135}$In and new $\beta$-decay branches of ${}^{134}$In
• Beta-delayed-neutron studies of ${}^{135,136}$Sb and ${}^{140}$I performed with trapped ions
• FRIB and the GW170817 Kilonova