The radiations of the ${\mathrm{U}}^{230}$ family have been investigated with an electromagnetic alpha-particle spectrograph and gamma-ray scintillation counters. The following alpha groups were found: ${\mathrm{U}}^{230}$—5.884 (67.2%), 5.813 (32.1%), 5.658 (0.7%); ${\mathrm{Th}}^{226}$—6.330 (79%), 6.220 (19%), 6.095 (1.7%), 6.029 (0.6%); ${\mathrm{Ra}}^{222}$—6.551; ${\mathrm{Em}}^{218}$—7.127 Mev. The following gamma rays were seen: ${\mathrm{U}}^{230}$—72 (0.75%), 158 (0.33%); 232 (0.24%); ${\mathrm{Th}}^{226}$—112 (4.8%); 131 (0.4%), 197 (0.40%), 242 (1.2%); ${\mathrm{Em}}^{218}$—609 kev (0.2%). The results are correlated into decay schemes, which are discussed with respect to current systematics and theory of complex alpha spectra and excited states of even-even nuclei.

• Received 23 May 1956

DOI:https://doi.org/10.1103/PhysRev.104.91