Internal Conversion Coefficients ofγRays inPu239

The $K$-conversion coefficients of the predominantly $M1\mathrm{}$ $\gamma$ rays of 209.7, 228.2, and 277.9 kev following the $\beta$ decay of ${\mathrm{Np}}^{239}$ have been measured using a curved crystal $\gamma$-ray spectrometer and a lens type $\beta$-ray spectrometer. The measured $K$-conversion coefficients are 1.76±0.30, 1.60±0.16, and 1.16±0.12, respectively. A limit of less than 10% has been placed on the admixture of $E2\mathrm{}$ in these radiations from a study of the $\frac{K}{L}$ and $L_{\mathrm{I}}:L_{\mathrm{II}}:L_{\mathrm{III}}$ conversion ratios. It is found, for $Z=94\mathrm{}$, that the measured conversion coefficients show better agreement with the $M1\mathrm{}$ predictions of Sliv who allowed for finite nuclear size than with Rose et al. who assumed a point charge nucleus. In addition, the $K$-conversion coefficients of the 254.7-, 285.5-, 316.2-, and 334.4-kev $\gamma$ rays of ${\mathrm{Pu}}^{23}$, have been measured to be 0.88±0.32, 0.11±0.02, 0.027±0.005, and 0.025±0.005, and the $L_{\mathrm{I}}$ and $L_{\mathrm{II}}$ conversion coefficients of the 106.4-kev $\gamma$ ray to be 0.062±0.007 and 0.071±0.007, respectively.