Precise Measurement of $\alpha_{\mathrm{K}}$ for the 39.76-keV E3 transition in 103Rh: Further Test of Internal Conversion Theory

We have extended our series of precision measurements of internal conversion coefficients (ICC) to include the 39.76-keV, \textit{E3} transition in $^{\mathrm{103}}$Rh. Our goal has been to test the Dirac-Fock ICC calculations, specifically with respect to the role of the atomic vacancy created in the conversion process. We prepared a sample from pure (natural) ruthenium chloride by converting the sample to ruthenium oxide, electrochemically depositing it on an aluminum backing, and subsequently activating it with thermal neutrons at the Texas A{\&}M TRIGA reactor for 20 hours. Decay spectra were then recorded for roughly 120 hours with a HPGe detector that has been precisely efficiency calibrated (\textpm .15{\%} relative precision). In the acquired spectra, all impurities were identified and corrected for accordingly. A program was written using the ROOT framework developed by CERN to extract the area of the 39.76-keV gamma-ray peak from $^{\mathrm{103}}$Rh, which partially overlapped the K$_{\mathrm{\alpha \thinspace }}$x-ray peaks$_{\mathrm{\thinspace }}$from a $^{\mathrm{153}}$Gd impurity. From the ratio of the 39.76-keV peak to the Ruthenium K x rays, we determined a preliminary value for the ICC: $\alpha _{\mathrm{k}}$(39.76)$=$134.6(19). This result agrees well with the theoretical calculation including the atomic vacancy, 135.2, and disagrees with the calculation excluding the vacancy, 127.4. This is consistent with our previous measurements, indicating that the atomic vacancy must be taken into account.