Half-Lives ofAt211andBi207

Least-squares analysis of alpha counting data has yielded a half-life of 7.214±0.007 hr for ${\mathrm{At}}^{211}$, in good agreement with previous results. From the gamma activity remaining after the decay of an extremely active ${\mathrm{At}}^{211}$ preparation, the half-life of ${\mathrm{Bi}}^{207}$ has been found to be 38±3 yr. This agrees with the highest of the values hitherto reported.