Abstract
A recent report on 209Po claimed to have made a determination of the 125-a half-life from measurements made over 0.8 % of one half-life. A careful reanalysis of the original data with a more complete and rigorous consideration of the underlying uncertainties demonstrates that this claim cannot withstand critical scrutiny. More importantly, this critique examines the larger issue as to what constitutes a valid half-life determination, and highlights that a careful and realistic analysis beyond the mere fitting of decay data to an exponential function is required for the measurement and reporting of half-life values.
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Notes
The ratio of two values Q = x 2/x 1 = exp [(−ln 2) L/T], separated in time by duration L with relative uncertainty ΔQ/Q, propagates to ΔT/T = 1/(λ L) (ΔQ/Q) for the relative uncertainty in the half-life T, with λ = ln 2/T.
The variables in the numerator and denominator for the “activity ratio” as given in Fig. 2 of PSB appear to be inverted on the axis label. It is believed that it should have appeared as A(t)/A(t 0) in order for the ratio to decrease as a function of time with the ratio equal to 100 % at t = t 0.
Certain commercial equipment, instruments, or materials are identified in this paper to foster understanding. Such identification does not imply recommendation by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.
Warping is symmetric in λ = (ln 2)/T about the fitted T, but asymmetric in T, which is exacerbated for short decay periods.
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Acknowledgments
We are indebted to Dr. Ryan Fitzgerald, research physicist at NIST, for his helpful insights on the general nature of the problem and critical commentary on this text. One of us (RC) extends a silent tribute to those few trying to keep the peer-review process legitimate.
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Collé, R., Collé, A.M. On the 209Po half-life error and its confirmation: a critique. J Radioanal Nucl Chem 308, 271–278 (2016). https://doi.org/10.1007/s10967-015-4307-y
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DOI: https://doi.org/10.1007/s10967-015-4307-y