Angular Correlation Measurements in the Decay ofHg197

Measurements of the ${e_K}^{-}$, ${e_L}^{-}$, and ${e_M}^{-}-\gamma$, ${e_{L+M}}^{-}-{e_K}^{-}$ and ${e_L}^{-}$, and $\gamma -\gamma$ angular correlation coefficients in sources of different chemical compositions in the $\frac{13}{2}\mathrm{}\left(M4\mathrm{}\right)\mathrm{}\frac{5}{2}\mathrm{}\left(E2\mathrm{}\right)\mathrm{}\frac{1}{2}$ cascade of 24-hour ${\mathrm{Hg}}^{197}$ have been carried out in a study of the effects of extranuclear fields on angular correlation measurements. Measurement of the $\gamma -\gamma$ correlation in dilute mercuric nitrate solutions yields $A_2=0.214\mathrm{}\pm 0.037$ in agreement with the theoretical value for this cascade. Solid $H_g{\left(\mathrm{N}{\mathrm{O}}_3\right)}_2$ sources show an attenuation of the $\gamma -\gamma$ coefficient, $g_2=0.51\mathrm{}\pm 0.16$. The ${e_K}^{-}-\gamma$ coefficients are attenuated relative to the theoretical coefficients by the factor $g_2=0.47\mathrm{}\pm 0.03$. The role of the effects of internal conversion on the attenuation of correlation coefficients is examined in terms of these measurements and those of other authors on ${\mathrm{Hg}}^{197}$, ${\mathrm{Hg}}^{199}$, and ${\mathrm{Ta}}^{181}$.