Short-Lived Isomeric States of Se83 and Ge77

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Abstract
Extractions of Br from neutron irradiated SeO3= solutions and of As from irradiated GeS3= solutions revealed the presence of short‐lived isotopes of Se83 and Ge77 decaying by β−‐emission to 2.4‐hr. Br83 and 40‐hr. As77, respectively. Direct observation of the radiations from a short‐lived Se, effected by measuring the activity of Se irradiated for 20 sec. through Al absorbers, led to a half‐life determination of 67±3 sec. and a β‐energy of 3.4 Mev. A γ‐ray was also observed. Similarly, a short‐lived Ge activity was found by irradiating GeS2 with neutrons for 20 sec. and measuring the activity through Al absorbers. The half‐life was determined to be 59±2 sec. and the β‐energy, 2.8 Mev. The agreement between the cross sections for formation of the 67‐sec. Se and the 2.4‐hr. Br83 from the short‐lived Se83 makes it probable that the 67‐sec. Se is genetically related to the 2.4‐hr. Br83. In a like manner it was shown that the 59‐sec. Ge is probably identical with the short‐lived Ge77. The presence of the 67‐sec. Se83 activity decaying by β−‐emission to 2.4‐hr. Br83 and the 59‐sec. Ge77 activity decaying to 40‐hr. As77 resolves the difficulty of the apparently high ``independent'' yields of Br83 and As77 in fission. A new Se activity of 17.5±0.3 sec. half‐life was also found. It appears to decay by emission of γ‐radiation of ∼150 Kev. The cross section for formation of this activity by neutron activation of Se is ∼0.6 barn.

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