The Gamma-Radiation from Long-Lived Yttrium

The gamma-radiation emitted by the 100-day yttrium isotope has been investigated. The momentum distribution of the recoil electrons from a thin paper radiator situated near the center of a cloud chamber falls into two groups. These groups correspond to gamma-ray energies of 0.95 ±{} 0.05 Mev and 1.92 ±{} 0.03 Mev. The relative number of quanta in the gamma-ray lines is one to 0.9, or approximately equal. Because the energy of one of the lines is half that of the other, a coincidence experiment must be done before a level diagram can be drawn with certainty.