Radiations of Uranium Y

The radioactivity of UY (${\mathrm{Th}}_{231}$) has been re-investigated. Samples were prepared by growth from ${\mathrm{U}}_{235}$ largely freed of ${\mathrm{U}}_{238}$, and absorption, decay, and coincidence experiments were run. The presence of the 210-kev beta-ray was re-confirmed, and a 35-kev gamma-ray 82 percent converted in the $L$ shell was discovered. The half-life of UY was determined as 25.5 hours.