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β-decay half-lives and β-delayed neutron emission probabilities for several isotopes of Au, Hg, Tl, Pb, and Bi, beyond N=126

R. Caballero-Folch et al.
Phys. Rev. C 95, 064322 – Published 23 June 2017

Abstract

Background: There have been measurements on roughly 230 nuclei that are β-delayed neutron emitters. They range from He8 up to La150. Apart from Tl210, with a branching ratio of only 0.007%, no other neutron emitter has been measured beyond A=150. Therefore, new data are needed, particularly in the region of heavy nuclei around N=126, in order to guide theoretical models and help understand the formation of the third r-process peak at A195.

Purpose: To measure both β-decay half-lives and neutron branching ratios of several neutron-rich Au, Hg, Tl, Pb, and Bi isotopes beyond N=126.

Method: Ions of interest were produced by fragmentation of a U238 beam, selected and identified via the GSI-FRS fragment separator. A stack of segmented silicon detectors (SIMBA) was used to measure ion implants and β decays. An array of 30 He3 tubes embedded in a polyethylene matrix (BELEN) was used to detect neutrons with high efficiency and selectivity. A self-triggered digital system is employed to acquire data and to enable time correlations. The latter were analyzed with an analytical model and results for the half-lives and neutron-branching ratios were derived by using the binned maximum-likelihood method.

Results: Twenty new β-decay half-lives are reported for Au204206, Hg208211,Tl211216,Pb215218, and Bi218220, nine of them for the first time. Neutron emission probabilities are reported for Hg210,211 and Tl211216.

Conclusions: The new β-decay half-lives are in good agreement with previous measurements on nuclei in this region. The measured neutron emission probabilities are comparable to or smaller than values predicted by global models such as relativistic Hartree Bogoliubov plus the relativistic quasi-particle random phase approximation (RHB + RQRPA).

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  • Received 19 January 2017

DOI:https://doi.org/10.1103/PhysRevC.95.064322

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Nuclear PhysicsGravitation, Cosmology & Astrophysics

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Vol. 95, Iss. 6 — June 2017

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