Small Deviations Observed in Beta Spectra: ${\mathrm{In}}^{114}$, ${\mathrm{Y}}^{90}$, and ${\mathrm{P}}^{32}$

The beta spectra of ${\mathrm{In}}^{114}$, ${\mathrm{Y}}^{90}$, and ${\mathrm{P}}^{32}$ (all of which decay by pure Gamow-Teller radiations) have been very carefully studied in a magnetic spectrometer. The Fermi-Kurie plots of all three spectra exhibit small deviations from linearity corresponding to an excess of low-energy electrons. All of the evidence indicates that the observed nonstatistical shapes represent the true spectra and are not the result of instrumental distortions. The Fermi-Kurie plots of these three isotopes can be linearized by a ($1+\frac{b}{W}$) correction factor (in addition to the once-forbidden, unique shape factor in the case of ${\mathrm{Y}}^{90}$).