A SEARCH FOR α-PARTICLES FROM THE DECAY OF Bi209

Abstract

A search for α-particles from Bi209has been carried out in Ilford C-2 bismuth-loaded nuclear emulsions maintained at 5 °C. for 3 years before development. Contrary to the findings of Faraggi and Berthelot (1951), Riezler and Porschen (1952), and Porschen and Riezler (1956), no evidence was obtained of α-particles in the 3 Mev. region which could be unambiguously attributed to bismuth, the experimental lower limit for the half-life thus determined being [Formula: see text] years. A detailed study of the energy available for the α-disintegration of Bi209by the method of reaction cycles gives a value of 2.93 ± 0.11 Mev. For this disintegration energy the half-life of Bi209predicted on the basis of α-decay theory and systematics is between 5 × 1019and 5 × 1022years.