The Decay ofAu197m

Abstract

The conversion electron spectra of ${\mathrm{Hg}}^{197m}$ and ${\mathrm{Au}}^{197m}$ have been re-examined. The 7.4-sec lifetime of ${\mathrm{Au}}^{197m}$ is found to be determined by a previously unresolved $E3\mathrm{}$ transition of 130.2 kev energy, whose transition probability is 3×${10}^{-3\mathrm{}}$ that expected on the Weisskopf estimate. The multipolarity of a "prompt" 77.4-kev transition in ${\mathrm{Au}}^{197}$ is found to be $M1+E2\mathrm{}$ (the ratio of magnetic to electric transitions being 1.5). A consistent decay scheme is presented. Some systematics of $L$ sub-shell conversion are discussed.