Decay ofAu200(48 min)

$\gamma$ radiation from the decay of ${\mathrm{Au}}^{200}$ has been measured in the energy range from 0.2 to 2 MeV with a 30-${\mathrm{cm}}^3$ coaxial-type lithium-drifted germanium detector. Fifteen $\gamma$ rays attributable to ${\mathrm{Hg}}^{200}$ were observed. Levels at 1570, 1593, and 1631 keV in ${\mathrm{Hg}}^{200}$ are strongly populated via $\beta$ decay. Weak feeding is suggested for levels at 1718, 1883, 1972, and 2061 keV. The $\beta$ branch to the 2+ level at 368 keV was found to be <8%; and the $\beta$ branches to the 4+ level at 947 keV, to the 0+ level at 1029 keV, and to the 2+ level at 1254 keV were found to be <0.2%, <0.5%, and <0.2%, respectively. The results favor spin and parity 1- for the ground state of ${\mathrm{Au}}^{200}$. Instead of a single 1225-keV line reported in the literature, a doublet with an energy difference of 37 keV was found. Also, instead of a single 1.6-MeV $\gamma$ ray known from scintillation spectrometer work, a group of $\gamma$ rays with energies between 1.5 and 1.7 MeV was observed.