Radioactive Decay ofCs137

The spins of the ground states of ${\mathrm{Cs}}^{137}$ and ${\mathrm{Ba}}^{137}$ are known to be 7/2 and 3/2, respectively. The shape of the 518-kev beta-ray spectrum has been measured and found to correspond to the correction factor $G^{\prime }={(W_0-W)}^2+A(W^2-1)$ in agreement with previous work. This is the shape predicted by the Fermi theory of beta-ray decay and the Gamow-Teller selection rules for a transition for which $\Delta I=\pm 2$ and there is a parity change. The internal conversion coefficient of the 663-kev gamma-ray has been measured and found to be 0.097, which is in agreement with the theoretical value for magnetic $2^4$-pole radiation.