The decay constant of radioactive decay is equal to the reciprocal value of the average → life time τ. Between the decay constant λ, the medium life time τ and the → half-life T the following relations exists: λ = τ-1 = T-1 ln 2
Winfried Koelzer, Nuclear Terms, Karlsruher Institut for Technologie KIT (Ed.), ISBN German print version 2001: 3-923704-32-1, Translation by Informationskreis KernEnergie (Berlin), Karlsruhe, Germany 2013. https://www.euronuclear.org/info/encyclopedia/pdf/ Nuclear_Glossary-%202013-02-13.pdf, (Nucl Sfty - Amer) {1011}