The Twice-Forbidden Transition ofCs137and the Law of Beta-Decay

The shape of the beta-spectrum of the direct 1.17 Mev, 8 percent abundant transition between the $g_{\frac{7}{2}}$ ground state of ${\mathrm{Cs}}^{137}$ and the $d_{\frac{3}{2}}$ ground level of ${\mathrm{Ba}}^{137}$ has been studied in detail in a magnetic spectrometer. The shape of the spectrum can be adequately described by a twice-forbidden factor, $C_{2T}$, resulting from the tensor form of interaction. Neither the axial vector form nor the combination $S-A-P$ are capable of accounting for the data.