Beta Decay ofY90m

An 0.620-MeV ${\beta }^{-}$ branch has been observed to compete with the previously reported gamma decay from the 3.14-h ${\mathrm{Y}}^{90m}$. The calculated values, derived from the shell model for the branching ratio [$\frac{(0.620-\mathrm{MeV}{\beta }^{-})}{(0.482-\mathrm{MeV}\gamma )}=1.16\mathrm{}\times {10}^{-3\mathrm{}}$] and the $log\mathrm{ft}$ (7.54) are compared with the experimental values of 3.8±1×${10}^{-3\mathrm{}}$ and 7.04±0.13, respectively. The small discrepancy is probably due to impurities in the shell-model configurations assumed for the transition.