A note on the half-life of 209Po

On the 209Po half-life error and its confirmation: a critique

“…2 shows a graphical depiction of the same. The findings from this residual analysis clearly demonstrates that there is no compelling evidence to support the Pomme et al [18] claim that their half-life measurement ''confirmed'' the earlier findings of Collé et al [7,15] on the error in the 209 Po half-life.…”

“…The origin of this belief is unknown to the original authors of the work; (3) The 2007 article by Collé et al [7] did not refer to the fitted value of 128.3 a as a half-life determination (clearly insisting that it was not), and never claimed that the reported fitting uncertainty of 7 a was an uncertainty on the half-life; (4) The ''robustness'', dependent on the 209 Po solution stability, and the ''trueness and repeatability'' of the LS spectrometry was treated in extenso in the Collé et al articles [6,7,15], while the PSB authors largely neglected to appreciate the rigor employed to ensure that ''the measurement method and data analyses used the identical protocols in all cases'' [7,15]; and (5) The NIST measurement methodology for the half-life determination was based on a unique LS spectral analysis procedure that is specific for the case of 209 Po decay (to account for the delayed 2-keV isomeric transition in 205 Pb and for the radiations accompanying the 0.45 % electron-capture branch to 209 Bi), and had absolutely no relation or relevance to the two references (Broda [21] and Pommé [22] ) cited in PSB. The PSB authors could have more usefully directed readers to any one of the three publications [6,7,15] (and even a pending one [16] referenced in [15] ) that describes the measurement method in great detail.…”

“…Despite the authors' statement [7] that the 128-a half-life value was not to be considered a new determination because it was only based on two datum points over about 12 years and that other possible effects and its attendant components of variance were unknown and unable to be evaluated, subsequent data evaluators [14] in deciding ''to take into account all scarce information available'' took the expedient of using the median of the two values (102 a and 128 a) and one-half the range of the values for the compiled 209 Po half-life: (115 ± 13) a.…”

“…This half-life result was merely the calculated value from two points assuming exponential decay. The authors [7] explicitly stated that this was not a new half-life determination and that the quoted uncertainty was not the uncertainty in a half-life. The estimate was given as evidence to strongly support the magnitude of the error in the 102-a half-life value.…”

“…Collé et al [7] reported finding a value of 128.3 a with a relative propagated uncertainty 1 of 5.5 % as obtained from two separate primary standardizations of the same solution conducted 11.7 a apart. This half-life result was merely the calculated value from two points assuming exponential decay.…”