Beta Spectrum ofTh233

The beta spectrum of ${\mathrm{Th}}^{233}$ has been measured in a ring-focus solenoidal spectrometer and was not found to exhibit an anomalous shape, as had been previously reported. The end point is 1.23±0.01 Mev in agreement with the earlier value. It is shown that ${\mathrm{Th}}^{233}$ decays predominantly to the ground state of ${\mathrm{Pa}}^{233}$. Halflife measurements yield a value of (22.4±0.1) min for ${\mathrm{Th}}^{233}$, somewhat shorter than the previously reported values.