Angular correlation measurements have been made on the 404-kev and 279-kev transitions following electron capture from 52-hour ${\mathrm{Pb}}^{203}$. The following directional correlations were measured: gamma-gamma, $K$ conversion electron-gamma, and gamma-$K$ conversion electron. The angular distribution of all measurements were of the form $W\left(\theta \right)=1+A{P}_2\left(cos\theta \right)$. The following results were obtained. For the $404\gamma -279K{e}^{-}$ correlation, $A=-0.052\mathrm{}\pm 0.015$, for the $279\gamma -404K{e}^{-}$ correlation, $A=-0.036\mathrm{}\pm 0.010$, and for the $404\gamma -279\mathrm{}\gamma$ correlation, $A=-0.151\mathrm{}\pm 0.010$. No effects due to perturbations of the intermediate state were found.

Using the well measured 279-kev $K$-conversion coefficient, the 404-kev $K$-conversion coefficient was determined to be 0.117±0.015 while the 680-kev $K$-conversion coefficient was determined to be 0.011±0.004. From the gamma-gamma angular correlation measurement result and the mixture ratio in the 279-kev transition determined by Stelson and McGowan, the mixture ratio in the 404-kev transition was determined to be ${\delta }_1=+0.043\mathrm{}\pm 0.010$. The Sliv value for the $K$-conversion coefficient for this mixture ratio is 0.147. The correlations involving conversion electrons rule out a $\frac{3}{2}\to \frac{3}{2}\to \frac{1}{2}$ transition. They indicate that the $M1\mathrm{}$ particle parameter in the 404-kev transition is about twice the theoretical prediction. The particle parameters for the 279-kev transition also do not agree with the theoretical predictions.

• Received 24 August 1959

DOI:https://doi.org/10.1103/PhysRev.117.818