Short-Lived Isomeric States of Se83 and Ge77

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.