Abstract
Following significant discrepancies observed when decay-correcting 122Sb γ-peak count rates to a reference time, we looked at the literature supporting the presently recommended 2.7238(2) d (1σ) 122Sb half-life value as the source of these discrepancies. Investigation revealed that the value was derived from an inconsistent dataset and was published without reporting details of the experiment nor the uncertainty budget. In this work we performed a new measurement of the 122Sb half-life by measuring the 122Sb decay of neutron-activated antimony samples using state-of-the-art γ-detection systems characterized in terms of efficiency drift and random pulse pile-up. The measurement was carried out in two different laboratories with the same method. The resulting 2.69454(39) d and 2.69388(30) d (1σ) 122Sb half-life values are in agreement at the evaluated 10–4 relative combined standard uncertainty level but are significantly lower (1.07% and 1.10% lower, respectively) than the preexisting recommended value.
Highlights
Antimony has two stable isotopes (121Sb and 123Sb) that can be detected by neutron activation via nuclear reactions 121Sb(n,γ)122Sb and 123Sb(n,γ)124Sb and quantified by counting γ-photons emitted by 122Sb and 124Sb at the interference-free energies 564.2 keV and 602.7 keV, respectively
We carried out two independent measurements of the 122Sb half-life
The resulting 122Sb half-life values were in agreement, there is a 1.1% relative difference with respect to the recommended value
Summary
Antimony has two stable isotopes (121Sb and 123Sb) that can be detected by neutron activation via nuclear reactions 121Sb(n,γ)122Sb and 123Sb(n,γ)124Sb and quantified by counting γ-photons emitted by 122Sb and 124Sb at the interference-free energies 564.2 keV and 602.7 keV, respectively. The stability of the decay corrected 124Sb 602.7 keV γ-peak count rate obtained with the same data did not show the same drift of the detection system. This experimental evidence suggested a potential bias affecting the presently recommended 2.7238(2) d 122Sb half-life, t1/2 [1], adopted for the decay correction. A literature review revealed that the recommended t1/2(122Sb) value is based on the most recent result of an inconsistent dataset published in 1990 [2] without reporting details on the experiment nor the uncertainty budget which are compulsory to support the claimed 1 0–4 relative standard uncertainty level [3]
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