The half-life of $^{221}$Fr in Si and Au at 4K and at mK temperatures

TL;DR

This study measures the half-life of $^{221}$Fr in different solid-state environments at cryogenic temperatures, finding no significant variation and providing a new precise half-life value.

Contribution

It presents the first systematic measurement of $^{221}$Fr half-life in Si and Au at mK and 4K temperatures, confirming environmental independence and refining the half-life value.

Findings

No half-life variation within 0.1% across environments

New precise half-life value of 286.1(10) seconds

Environmental factors do not affect $^{221}$Fr alpha decay

Abstract

The half-life of the $\alpha$ decaying nucleus $^{221}$Fr was determined in different environments, i.e. embedded in Si at 4 K, and embedded in Au at 4 K and about 20 mK. No differences in half-life for these different conditions were observed within 0.1%. Furthermore, we quote a new value for the absolute half-life of $^{221}$Fr of t$_{1/2}$ = 286.1(10) s, which is of comparable precision to the most precise value available in literature.