THE DECAY OF Re186 AND Re188

Abstract

The energies and intensities of 13 gamma rays in Re188 have been measured by studying their external conversion spectra with a high resolution beta-ray spectrometer. An analysis of the beta-ray spectrum reveals groups with end points 2116 kev. (79%) and 1961 kev. (20%), and several low energy groups whose total intensity is of the order of 1%. The observed data can be consistently accounted for in terms of a decay scheme involving the following levels of OS188: 0.0, 155.0, 633, 1086, 1306, 1461, 1765, 1941, and 1958 kev. This scheme is firmly supported by coincidence measurements. The spins of the first three levels listed are 0+, 2+, and 2+ and that of the 1461 kev. level is probably 0+.The decay of Re186 is accompanied by gamma rays of the following energies and quantum intensities: 122.9 kev. (0.6%), 137.2 kev. (10%), 630.8 kev. (0.024%), and 768.2 kev. (0.024%). These values are in good agreement with those quoted in the literature, except for the intensities of the last two radiations.