Precise measurement of the emission probability of the 543 keV γ ray of 199Pt

199Pt has been produced by neutron irradiation of enriched 198Pt (95.71%) metal powder, and precise measurements have been made of the γ-ray emission probabilities by means of 4πβ−γ coincidence apparatus and a live-timed two-dimensional data-acquisition system. Daughter 199Au decays with a half-life of 3.139 d, and therefore the measured disintegration rate had to be corrected. The absolute emission probability of the 543.0 keV γ ray was determined to be 0.1174±0.0007 from the γ-ray intensity and the corrected disintegration rate.