Yttrium-91 was observed to decay with a half-life of 57.5±0.5 days. In addition to the 1.55-Mev beta transitions, 0.22±0.01 percent of the ${\mathrm{Y}}^{91}$ decay consists of a 0.36±0.02-Mev beta group in coincidence with a 1.190±0.005-Mev gamma ray.

• Received 6 December 1954

DOI:https://doi.org/10.1103/PhysRev.98.58