A new low-uncertainty measurement of the 31Si half-life

Half-life values are widely used in nuclear chemistry to model the exponential decay of the activity of radionuclides. The analysis of existing half-life data values reveals a general lack of information on the performed experiments and, in a few cases, an almost complete absence of uncertainty budgets. This is the situation for 31Si, the radionuclide produced via neutron capture reaction recently used to quantify trace amounts of 30Si in a sample of the 28Si-enriched material produced for the determination of the Avogadro constant. In particular, the now recommended 157.36(26) min value is the weighted average of ten data acquired between the 40s and the 90s and published without a detailed discussion of the uncertainty budget. In order to improve the 31Si half-life value we carried out repeated observations of the 31Si decay rate via γ-ray spectrometry measurements. This paper reports the result we obtained, including details of the experiment and the evaluation of the uncertainty.