A new low uncertainty measurement of the 111Ag half-life

Following a discrepancy observed between the presently recommended 7.45(1) days (1 σ ) 111 Ag half-life and the two most recent values reported in the literature, we carried out a new determination by measuring the decay of a 111 Ag sample using state-of-the-art γ-ray detection systems fully characterized for their long-term efficiency stability. The measurement was carried out by recording two consecutive observation sequences lasting about 33 days each and performed with two detection systems working under different measurement conditions to test the robustness of the adopted method. The resulting 7.4236(11) days (1 σ ) value is not in agreement with the recommended value and confirms the observed discrepancy. A comprehensive uncertainty budget including the contribution due to counting statistics, pulse pile-up, detector stability, decay correction and γ-peak fitting was produced to support the achieved 1.5 × 10 -4 relative standard uncertainty, which is more than one order of magnitude lower than the uncertainties found in literature.