The decays of ${}_{}{}^{236}{}_{}{}^{}\mathrm{Th}$ and its ${}_{}{}^{236}{}_{}{}^{}\mathrm{Pa}$ daughter were studied by $\gamma$-ray spectroscopy. By means of radiochemical methods and a continuous separation technique pure sources of parent and daughter were prepared so that each was free (or almost free) of the other. For ${}_{}{}^{236}{}_{}{}^{}\mathrm{Th}$, 14 of the 17 observed $\gamma$ rays are new; for ${}_{}{}^{236}{}_{}{}^{}\mathrm{Pa}$ 16 new $\gamma$ rays were found. Absolute intensities of all the $\gamma$ rays were determined with the aid of $4\pi$ beta measurements on ${}_{}{}^{236}{}_{}{}^{}\mathrm{Pa}$. A new decay scheme is proposed for ${}_{}{}^{236}{}_{}{}^{}\mathrm{Th}$ and a considerably expanded one is given for ${}_{}{}^{236}{}_{}{}^{}\mathrm{Pa}$. The half-lives determined are 37.5±0.2 min for ${}_{}{}^{236}{}_{}{}^{}\mathrm{Th}$ and 9.1±0.1 min for ${}_{}{}^{236}{}_{}{}^{}\mathrm{Pa}$.

• Received 7 November 1983

DOI:https://doi.org/10.1103/PhysRevC.29.985