Confirmation of 20% error in the (209)Po half-life.

First results of a half-life measurement of (209)Po show 20% discrepancy with the formerly recommended value of 102 (5) years, which was based on a single experiment performed in 1956. After one year of measurement, a statistical uncertainty on T1/2 of 3.5% has been reached and effects of long-term instability are assumed to be less than 5%. The preliminary half-life value obtained in this work, 120 (6) years, supports the newly determined value of 125.2 (33) years by Collé et al. (2014). The 20% error in the half-life has an impact on numerous measurements in which aged (209)Po solutions were used as a tracer.