Directional correlation measurements have been made on the 356-82 kev, 301-82 kev, and 80-82 kev gamma-gamma cascades in ${\mathrm{Cs}}^{133}$ following the decay of 8-year half-life ${\mathrm{Ba}}^{133}$ with a coincidence scintillation spectrometer using NaI detectors. The observed correlation functions are: $W\left(\theta \right)=1+(0.042\mathrm{}\pm 0.005)P_2\left(cos\theta \right)-(0.0041\mathrm{}\pm 0.0038)P_4\left(cos\theta \right),$ $W\left(\theta \right)=1-(0.0257\mathrm{}\pm 0.011)P_2\left(cos\theta \right)-(0.0002\mathrm{}\pm 0.008)P_4\left(cos\theta \right),$ and $W\left(\theta \right)=1+(0.0487\mathrm{}\pm 0.017)P_2\left(cos\theta \right)+(0.0011\mathrm{}\pm 0.012)P_4\left(cos\theta \right),$ respectively, for the three cascades. These gamma-gamma directional correlations were found to be consistent with spin assignments of ${\frac{7}{2}}^{+}$, ${\frac{5}{2}}^{+}$, ${\frac{3}{2}}^{+}$, ${\frac{3}{2}}^{+}$, and ${\mathrm{½}}^{+}$ to the levels at the ground state, 82-kev, 162-kev, 383-kev, and 438-kev in ${\mathrm{Cs}}^{133}$. The probable assignment of the multipolarities for different gamma rays is as follows: The 356-kev gamma ray is pure $E2\mathrm{}$. The 82-kev gamma ray is a mixture of (96.5±0.5)% $M1\mathrm{}$ and (3.5±0.5)% $E2\mathrm{}$ with ${\delta }_{82}=-0.190\mathrm{}\pm 0.014$. The 301-kev gamma ray can have one of two possible mixtures: either ${\delta }_{301}=+0.123\mathrm{}\pm 0.004$ with a mixture of (98.5±1.0)% $M1\mathrm{}$ and (1.5±1.0)% $E2\mathrm{}$, or ${\delta }_{301}=-3.98\mathrm{}\pm 1.02$ with a mixture of (6±2)% $M1\mathrm{}$ and (94±2)% $E2\mathrm{}$. The value of ${\delta }_{301}=-3.98\mathrm{}\pm 1.02$ is more probable. The 80-kev gamma ray is also found to have two possible values of ${\delta }_{80}$: either ${\delta }_{80}=+0.47\mathrm{}\pm 0.09$ with a mixture of (82±6)% $M1\mathrm{}$ and (18±6)% $E2\mathrm{}$, or ${\delta }_{80}=+7.0\mathrm{}$ with a mixture of (2.0±1.5)% $M1\mathrm{}$ and (98.0±1.5)% $E2\mathrm{}$.

• Received 23 November 1960

DOI:https://doi.org/10.1103/PhysRev.122.549