average life

in nuclear chemistry
Defined for an atom or nuclear system in a specified state. For an exponentially decaying system, it is the average time for the number of atoms or nuclei in a specified state to decrease by a factor e. Synonymous with mean life.
PAC, 1982, 54, 1533. 'Glossary of terms used in nuclear analytical chemistry (Provisional)' on page 1536 (https://doi.org/10.1351/pac198254081533)