On the Validity of the Geiger-Nuttall Alpha-Decay Law and its Microscopic Basis

TL;DR

This paper investigates the Geiger-Nuttall law's microscopic basis, revealing its empirical coefficients have physical meaning and identifying its limitations when the alpha formation probability varies non-linearly with neutron number.

Contribution

It provides a microscopic interpretation of the GN law's coefficients and demonstrates its limited validity beyond specific experimental data sets.

Findings

Empirical coefficients in the GN law have deep physical meaning.

The GN law fails when alpha formation probability depends non-linearly on neutron number.

Significant deviations observed in neutron-deficient $^{186}$Po decay predictions.

Abstract

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 $^{186}$Po, the difference between the experimental half-life and that predicted by the GN Law is as large as one order of magnitude.