Spontaneous double alpha decay: First experimental limit and prospects of investigation

TL;DR

This paper investigates the possibility of observing spontaneous double alpha decay in natural nuclides, providing the first experimental limit on its half-life for 209Bi and discussing the challenges due to extremely long predicted half-lives.

Contribution

It establishes the first experimental limit on double alpha decay half-life for 209Bi and evaluates the prospects of detecting such decay based on theoretical estimates.

Findings

First experimental limit: T1/2 > 2.9e20 years for 209Bi

Theoretical half-life estimates are around 1e33 years or more

Detection prospects are very unlikely due to extremely long half-lives

Abstract

Nuclear decays with simultaneous emission of two alpha particles are energetically possible for a number of nuclides. Prospects of searching for such kind of decay for nuclides present in the natural isotopic composition of elements are discussed here. The first experimental limit on half-life for 2alpha decay is set for 209Bi as T1/2 > 2.9e20 y at 90% C.L., using the data of work [P. de Marcillac et al., Nature 422 (2003) 876]. Theoretical T1/2 estimations for the process are also given. Using these values, which are on the level of 1e33 y or more, one can conclude that the prospects of experimental observation of 2alpha decay are very pessimistic.