A new determination of the 209Po half-life

A substantial 25% error in the then-known and accepted (102 +/- 5) year half-life of Po-209 was reported on in 2007. This error was detected from decay data from two separate primary standardizations of a Po-209 solution standard, which were performed approximately 12 years apart. Despite author claims that this observation was not a new half-life determination, it was nevertheless included in subsequent nuclear data evaluations and compilations to obtain a currently tabulated value of (115 +/- 13) a, computed from the median and range of the two half-life reports. A third primary standardization on the identical Po-209 solution has since been performed to derive a new half-life value of (125.2 +/- 3.3) a. This half-life determination was obtained from 30 distinct data sets over a period of 20.7 years, encompassing over 700 liquid scintillation measurements with nearly 50 counting sources all prepared from the same solution, and as obtained over a very broad range of measurement conditions (composition of cocktails, characteristics of counters, time sequencing) during five periods in 1993, 1994, 2005, and 2013.