Beta Spectrum ofBi212(ThC)

The beta spectrum of ${\mathrm{Be}}^{212}$ was measured by using a short magnetic-lens beta spectrometer. ${\mathrm{Pb}}^{212}$ in equilibrium with its decay products was used as a source. The spectrum of ${\mathrm{Bi}}^{212}$ was separated from the other component spectra by measuring the coincidences between the beta spectrum and the alpha particles from ${\mathrm{Po}}^{212}$ (the nucleus formed after the beta decay of ${\mathrm{Bi}}^{212}$) emitted with the half-life of 3×${10}^{-7\mathrm{}}$ sec.