Short-Lived Isomers of Nuclei

Abstract

A search for short-lived nuclear isomers of half-lives between ${10}^{\ensuremath{-}6}$ and ${10}^{\ensuremath{-}3}$ sec. has been performed using the method of delayed coincidences between two Geiger counters. A short-lived isomer is detected by the measurement of the time lapsed between $\ensuremath{\beta}$-decay and $\ensuremath{\gamma}$- (or internal conversion electron) emission. Out of 60 nuclei investigated, 4 short-lived isomeric states were found. These are: ${\mathrm{Ta}}^{181*}$ (22 \ensuremath{\mu}sec.), ${\mathrm{Re}}^{187*}$ (0.65 \ensuremath{\mu}sec.), ${\mathrm{Tm}}^{169*}$ (1 \ensuremath{\mu}sec.), and ${\mathrm{Tm}}^{171*}$ (2.5 \ensuremath{\mu}sec.).