Precise Measurements of the Internal Conversion Coefficient of $^{\mathrm{\mathbf{111m}}}$Cd Isomer

The theoretical Internal Conversion Coefficient, $\alpha_{\mathrm{K}}$, for the 150 keV E3 transition in $^{\mathrm{111m}}$Cd depends on the treatment of the atomic vacancy. If the atomic vacancy is taken into consideration, the $\alpha_{\mathrm{K}}$ value equals to 1.450, while the $\alpha_{\mathrm{K}}$ value is 1.425 when the vacancy is neglected. In an 1987 publication, the $\alpha_{\mathrm{K}}$ was determined to be 1.29 $\pm$ 0.11, which agrees with neither value. To investigate this discrepancy, we conducted an experiment to remeasure the $\alpha _{\mathrm{K}}$ of $^{\mathrm{111m}}$Cd. By using a 99{\%} enriched $^{\mathrm{110}}$Cd sample and activating it with thermal neutrons, we produced the desired $^{\mathrm{111m}}$Cd isomer. With a very well calibrated High Purity Germanium detector, the gamma-rays as well as the X-rays corresponding to the 150 keV transition were observed, and their relative intensities measured. Our preliminary $\alpha_{\mathrm{K}}$ value results is 1.458 $\pm$ 15, which agrees with the theoretical $\alpha _{\mathrm{K}}$ value that includes the atomic vacancy, and disagrees with the no-vacancy calculation.