Gamma-ray emission from 84–87Se and 85–88Br isotopes

Abstract

Abstract Gamma-ray emission from 84 Se, 85 Se, 86 Se, 87 Se, 85 Br, 86 Br, 87 Br and 88 Br has been studied over the energy range 300–7100 keV using a Ge(Li) detector. Selenium isotopes were separated from a mixture of fission products using high-speed radiochemistry and the bromine daughters allowed to grow in. The large difference in half-life between 86 Se and 87 Se was used to distinguish between 86 Br (54 sec) and 87 Br (55 sec). New gamma lines have been assigned to selenium isotopes as follows: a line at 498·5 ± 0·6 keV to 84 Se; thirty-seven lines to 85 Se; seven lines to 86 Se; two lines to 87 Se. At least 98 per cent of decay of 84 Se is found to go via the ground state of 84 Br (31·7 min). A partial decay scheme is proposed for 85 Se. The half-lives of 85 Se and 86 Se were found to be 31·4 ± 1·0 sec and 14·4 ± 1·0 sec, respectively. A line at 832 keV previously assigned to 85 Br has been shown to be due to 90m Rb + 90 Rb. Data for 86 Br are generally in agreement with previous findings but three new lines were observed at 6161·5 ± 2·0, 6722 ± 3 and 6768·3 ± 1·5 keV, which must represent new levels in 86 Kr. Only the strongest lines were observed in the decay of 87 Br and 88 Br and these are generally in agreement with previous work.