Nuclear Transitions inAu197

The energy of the hardest gamma ray emitted following ${\beta }^{-}$ decay of the ground state of ${\mathrm{Pt}}^{197}$ (18 h) has been measured in a lithium-drifted germanium detector to be 268 keV. A 279-keV gamma ray was resolved which decayed in intensity with the 78-min half-life of the isomeric level of ${\mathrm{Pt}}^{197}$. The $K$-shell conversion coefficient of the 191-keV transition has been experimentally determined as 1.59±0.07, suggesting an $E0\mathrm{}$ component, and that the spin and parity of the 268-keV level in ${\mathrm{Au}}^{197}$ are ½+. Previously reported gamma rays in the decay of these platinum isomers at 155 and 202 keV are shown to arise from the presence of ${\mathrm{Au}}^{199}$, formed in the ${\beta }^{-}$ decay of ${\mathrm{Pt}}^{199}$.