Decay ofAg108m

Abstract

The decay of the long-lived isomer (g5 yr) of ${\mathrm{Ag}}^{108}$ has been investigated with scintillation and proportional-counter spectrometers employing coincidence techniques. Conversion-electron measurements with a high-transmission orange-type spectrometer and a high-resolution $\ensuremath{\pi}\sqrt{2}$ double-focusing spectrometer together with gamma-gamma angular-correlation measurements served to establish the multipolarities of most of the observed transitions. ${\mathrm{Ag}}^{108m}$ has been found to decay 8.5% of the time via a two-step isomeric cascade consisting of a 30.4-keV $M4$ transition followed by a 79.4-keV $E1$ transition. The remaining 91.5% of the decays proceed by an electron-capture transition to a 1770-keV level in ${\mathrm{Pd}}^{108}$. This level then decays to the ground state of ${\mathrm{Pd}}^{108}$ via a 722.7\ifmmode\pm\else\textpm\fi{}1.0 keV, 613.9\ifmmode\pm\else\textpm\fi{}0.6 keV, 433.6\ifmmode\pm\else\textpm\fi{}0.5 keV triple gamma cascade. Two excited states at 79.4\ifmmode\pm\else\textpm\fi{}0.5 and 109.8\ifmmode\pm\else\textpm\fi{}0.5 keV are established in ${\mathrm{Ag}}^{108}$, with proposed spins and parities of 2- and 6+, respectively. The half-life of the 79-keV level has been shown to be \ensuremath{\le} ${10}^{\ensuremath{-}9}$ sec. The spins and parities of the 1770- and 1048-keV levels in ${\mathrm{Pd}}^{108}$ are assigned as 6+ (possibly 5+) and 4+, respectively.