Spins of Excited States ofTl208from Alpha-Gamma Angular Correlations

Measurements have been made of the angular correlations of the 5.60-MeV $\alpha$ ray occurring in the decay of ${\mathrm{Bi}}^{212}$ to the fourth excited state of ${\mathrm{Tl}}^{208}$ with the subsequent 452-keV $\gamma$ ray, and of the 5.76-MeV $\alpha$ ray occurring in the decay to the second excited state with the subsequent competing 288- and 328-keV $\gamma$ rays. The detectors employed were a 2-in.×2-in. NaI (Tl) crystal for $\gamma$ rays, and a silicon surface barrier counter for $\alpha$ rays. The results of the angular correlation measurements were