Lifetime measurements of 214 Po and 212 Po with the CTF liquid scintillator detector at LNGS

We have studied the α -decays of 214 Po into 210 Pb and of 212 Po into 208 Pb tagged by the coincidence with the preceding β -decays from 214 Bi and 212 Bi, respectively. The 222 Rn, 232 Th, and 220 Rn sources used were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of 214 Po is (236.00 ± 0.42(stat) ± 0.15(syst)) μ s and that of 212 Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results, obtained from data with signal-to-background ratio larger than 1000, reduce the overall uncertainties and are compatible with previous measurements.