On the Half-Lives of Potassium, Rubidium, Neodymium and Samarium

The long apparent half-lives of K, Rb and Nd are in striking disagreement with theory. To relieve this discrepancy, at least in part, the suggestion has often been made that their activities are due to isotopes of small abundance, having half-lives small in comparison with the apparent ones. Using data on the relative abundance of the elements, it is shown that the half-life of the active fraction of K is greater than 10⁷ years, and that the active fractions of Rb, Nd and Sm have half-lives greater than 10⁸ years. It is pointed out that these activities may be caused by small radioactive fractions of well-known isotopes; RaD and stable Pb(210) constitute a similar case. Data are presented which show that it is possible for the active portions of Nd and Sm to be genetically connected.