Investigation of the Beta-Spectra of Be10, K40, Tc99, and Cl36

Abstract

The beta spectra of ${\mathrm{Be}}^{10}$, ${\mathrm{K}}^{40}$, ${\mathrm{Tc}}^{99}$, and ${\mathrm{Cl}}^{36}$ were investigated with the Columbia University solenoidal spectrometer and it was found that each exhibited a forbidden shape. An analysis of the spectra yields the following results. The spectrum of ${\mathrm{Be}}^{10}$, for which $\Delta J=3\mathrm{}$, can be explained equally well by $2T$ or $2A$ for no parity change and by $3T$ or $3V$ if the parity does change. Similarly, the spectrum of ${\mathrm{K}}^{40}$, for which $\Delta J=4\mathrm{}$, can be accounted for by $3T$ or $3V$ if the parity changes and by $4T$ or $4V$ for no parity change. $\Delta J=2\mathrm{}$ for the decays of both ${\mathrm{Tc}}^{99}$ and ${\mathrm{Cl}}^{36}$. These spectra can be explained only by $2T$ or $2V$ with values for $k^2$ of 45 for ${\mathrm{Tc}}^{99}$ and 18 for ${\mathrm{Cl}}^{36}$ ($k^2={\left|A_{\mathrm{ij}}\right|}^2÷{\left|T_{\mathrm{ij}}\right|}^2$). If the true interaction prevailing in beta-decay is but a single one of the five linearly independent interactions, then it follows from these spectrum analyses that it must be the tensor interaction. A linear combination of tensor with one or more of the other interactions is possible. It seems, however, that more information than is provided by spectrum studies alone is necessary to determine the exact form of such a linear combination.