The beta spectra of ${\mathrm{In}}^{114}$, ${\mathrm{P}}^{32}$, and ${\mathrm{Y}}^{90}$ have been studied closely in an intermediate-image beta-ray spectrometer and compared to theoretical predictions in terms of a linear shape factor of the form ($1+aW$). The values obtained for $a$ were $\frac{(+0.0036\mathrm{}\pm 0.0021)}{m{c}^2}$ for ${\mathrm{In}}^{114}$, $\frac{(-0.0133\mathrm{}\pm 0.0011)}{m{c}^2}$ for ${\mathrm{P}}^{32}$, and $\frac{(-0.0047\mathrm{}\pm 0.0008)}{m{c}^2}$ for ${\mathrm{Y}}^{90}$, all for electron kinetic energies from about 200 kev up to near the maximum beta energies. Tests were made to give indications for spectrometer fidelity. Because of the linearity of the shape-factor plots and the similarity in energy range, the comparative results from ${\mathrm{In}}^{114}$, ${\mathrm{P}}^{32}$, and ${\mathrm{Y}}^{90}$ are taken as a definite indication that for at least two of these activities the shape factors have nonzero slopes, irrespective of questions of instrumental fidelity.

• Received 7 November 1960

DOI:https://doi.org/10.1103/PhysRev.122.172