Search for parity mixing in the ${}_{}{}^{93}{}_{}{}^{}\mathrm{Tc}$ ${17/2}^{-}$ isomer: measurements of internal conversion coefficients

The internal conversion coefficients were measured for several transitions in ${}_{}{}^{93}{}_{}{}^{}\mathrm{Tc}$ with an electron spectrometer and a Ge(Li) detector. The ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}(\alpha ,p2n)$ reaction was used to study the decay of the isomeric $\tau =15\mathrm{}$ μsec $\frac{17}{2}$ level at 2185.3 keV as well as the decay of the prompt ${\frac{17}{2}}^{+}$ level at 2185.0 keV. Due to parity mixing the wave function for the $\frac{17}{2}$ isomeric level may have the form $|{\frac{17}{2}}^{-}〉+\alpha |{\frac{17}{2}}^{+}〉$ where $\alpha$ is small. The experimental $K$-shell conversion coefficients for the $\frac{17}{2}\to {\frac{13}{2}}^{+}$ and ${\frac{17}{2}}^{+}\to {\frac{13}{2}}^{+}$ transitions imply $\frac{\Gamma (E2,\frac{17}{2}\to {\frac{13}{2}}^{+})}{\Gamma (E2+M2+E3,\frac{17}{2}\to {\frac{13}{2}}^{+})}<~0.33$. The energy difference between the prompt and delayed $\gamma$-ray transitions to the ${\frac{13}{2}}^{+}$ level was measured to be 0.32 ± 0.03 keV. These results imply $\left|〈{\frac{17}{2}}^{+}\right|H_{\mathrm{pv}}\left|{\frac{17}{2}}^{-}〉\right|<~0.13$ eV for the matrix element of the parity violating Hamiltonian.

NUCLEAR REACTIONS ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}(\alpha ,p2n)$, $E=43\mathrm{}$ MeV measured pulse beam electronic timing, $I_{\mathrm{ce}}$, $I_{\gamma }$, $E_{\gamma }$; deduced ${\alpha }_K$, $\gamma$ multipolarity, parity mixing. Enriched target, electron spectrometer, Si(Li) and Ge(Li) detectors.