Odd-Parity Rotational Bands in Even-Even Nuclei

The low-intensity radiations accompanying the alpha decay of ${\mathrm{Th}}^{230}$ and ${\mathrm{Th}}^{228}$ have been studied with a scintillation and coincidence spectrometer. In addition, the alpha-particle spectrum of ${\mathrm{Th}}^{228}$ has been reexamined using a magnetic spectrograph. New gamma rays of 253 kev (8×${10}^{-4\mathrm{}}$%), 110 kev (1×${10}^{-4\mathrm{}}$%), 206 kev (5×${10}^{-6\mathrm{}}$%), and 235 (5×${10}^{-6\mathrm{}}$%) have been found associated with ${\mathrm{Th}}^{230}$ decay. A new gamma ray of 205 kev (0.03%) has been found in ${\mathrm{Th}}^{228}$ decay, and also a fifth alpha group populating a level 289 kev above the ground state was observed in an abundance of 0.03%. A new level at 416 kev in ${\mathrm{Ra}}^{226}$ suggested by these data and the coincidence measurements has been interpreted as the 6+ member of the ground-state rotational band. The remaining new levels have been assigned as 3- and 5- members of rotational bands based on the 1- states previously observed in both ${\mathrm{Ra}}^{226}$ and ${\mathrm{Ra}}^{224}$.