Complex Alpha Spectra of Radiothorium (Th228) and Thorium-X (Ra224)

The alpha and gamma spectra of ${\mathrm{Th}}^{228}$ have been studied with an alpha-particle spectrograph and gamma-ray scintillation counters. Thorium 228 has alpha groups of 5.421 (71 percent), ${5.338}_5$ (28 percent), 5.208 (0.4 percent), and 5.173 Mev (0.2 percent), and gamma rays of 89 (1.6 percent), 137 (0.26 percent), 169 (0.09 percent), and 212 kev (0.27 percent). Spins and parities are assigned to the energy levels defined by the alpha groups, and the results are evaluated with respect to the developing theory and systematics of complex alpha spectra.