Transient events observed since 1980 by the Gamma-Ray Spectrometer experiment on the Solar Maximum Mission satellite (SMM) have been identified with radiation emitted from 18 different Soviet nuclear reactor-powered satellites. Most of these satellites are similar to Cosmos 954 and 1402 which reentered the atmosphere. Gamma radiation from these satellites was detected when they passed within about 400 to 500 kilometers of SMM. Positron annihilation line radiation (511 kiloelectron volts) and charged-particle events were detected when SMM encountered clouds of positrons and electrons emitted by these satellites and stored up to tens of minutes in the geomagnetic field. The rate of these events varied from about 1 in 5 days to over 30 per day and was strongly dependent on the operating altitudes of the Cosmos satellites and density of the upper atmosphere.
The radioactive decay of Se 83 produced by Se 82 (n,y) has been investigated experimentally, leading to a proposed level scheme for Br 83 . The half-life of the long-lived decay was determined to be 22.6=b0.2 min, and the 70-sec half-life of Se 83m was confirmed. For the long-lived decay, the various coincidence studies lead to a proposed decay scheme incorporating 29 y rays and involving excited levels in Br 83 at 356,
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