IDENTIFICATION OF PT-185 A-ACTIVITY AND STUDY OF AU-185 A-DECAY

The alpha-decay of Pt-185 has been observed for the first time and alpha-decay branching ratios have been determined for 185Au and 185Pt by use of an on-line isotope separator. A single alpha-decay line at 4444 +/- 10 keV has been shown to result from the decay of 185Pt. The current data are insufficient to determine which of the long-lived states of 185Pt decays via alpha-emission. The alpha branching deduced from the alpha, gamma, and x-ray data taken simultaneously is [(1.0 +/- 0.4) x 10(-3)]% if the alpha comes from the 33.0-min isomer, or [(5.0 +/- 2.0) x 10(-3)]% if the alpha comes from the 70.9-min ground state of 185Pt. In either case the transition is an unhindered one. Two lines at 5069 +/- 10 and 4826 +/- 10 keV, with relative intensities of 100 and 0.16, are attributed to the alpha-decay of 185Au and the deduced alpha-branching is (0.7 +/- 0.1)%. The hindrance factors are 0.4 for the 5069-keV, and 8.8 for the 4826-keV transitions.