Alpha-particle and electron capture decay of 209Po

Gamma-ray and Kα X-ray emissions have been measured from a very pure 209Po source containing less than 0.13% 208Po activity and no detectable 210Po (≤ 2 × 10−4%). The alpha-particle emission rate for this source has previously been determined. Data are presented that confirm alpha decay to the 205Pb excited level at 262.8 keV, with an alpha-particle emission probability (±standard uncertainty) of 0.00559±0.00008. The ratio of K-shell electron capture to total electron capture for the second forbidden unique electron capture decay to the 896.6 keV level in 209Bi was determined to be 0.594±0.018. The electron capture decay fraction was found to be 0.00454±0.00007, while the probabilities per decay for the 896.6, 262.8, and 260.5 keV gamma rays and the Bi Kα and Pb Kα X-rays were measured as 0.00445±0.00007, 0.00085±0.00002, 0.00254±0.00003, 0.00202±0.00005, and 0.00136±0.00005, respectively.