On the validity of the Geiger-Nuttall alpha-decay law and its microscopic basis

The Geiger-Nuttall (GN) law relates the partial alpha-decay half-life with the energy of the escaping alpha particle and contains for every isotopic chain two experimentally determined coefficients. The expression is supported by several phenomenological approaches, however its coefficients lack a fully microscopic basis. In this paper we will show that: (1) the empirical coefficients that appear in the GN law have a deep physical meaning, and (2) the GN law is successful within the restricted experimental data sets available so far, but is not valid in general. We will show that, when the dependence of logarithm values of the alpha formation probability on the neutron number is not linear or constant, the GN law is broken. For the alpha decay of neutron-deficient nucleus Po-186, the difference between the experimental half-life and that predicted by the GN law is as large as one order of magnitude. (C) 2014 The Authors. Published by Elsevier B.V.