The ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}({}_{}{}^6{}_{}{}^{}\mathrm{Li}, 3n\gamma ){}_{}{}^{93}{}_{}{}^{}\mathrm{Tc}$ reaction has been used in conjunction with pulsed-beam $\gamma$, $\gamma -\gamma$ coincidence, and $\gamma$ angular distribution measurements to investigate a proposed $\left[{\left({\mathrm{g}}_{\frac{9}{2}}\right)}^4{p}_{\frac{1}{2}}\right]{\frac{17}{2}}^{-}$ isomer in ${}_{}{}^{93}{}_{}{}^{}\mathrm{Tc}$. The isomeric level was found at 2185 keV on the basis of its decay properties and lifetime. The mean lifetime of the ${17/2}^{-}$ isomeric level was measured to be $\tau =15.2\mathrm{}\pm 1.0$ μsec. The level decays by a 39.7-keV $E2\mathrm{}$ branch (73.7±1.0%) to the 2145-keV ${13/2}^{-}$ level and by a 750.7-keV $\frac{M2\mathrm{}}{E3\mathrm{}}$ branch (26.3±1.0%) to the 1434-keV ${13/2}^{+}$ level. An experimental $B\left(E2\mathrm{}\right)\mathrm{} [{\frac{17}{2}}^{-}\to {\frac{13}{2}}^{-}]=11.4\mathrm{}\pm 0.9$ ${\mathit{e}}^2$${\mathrm{fm}}^4$ is obtained for the $E2\mathrm{}$ branch, implying an effective charge of $e_p=2.49\mathrm{}\pm 0.10$. To explore possible parity mixing between the nearly degenerate ${17/2}^{-}$ and ${17/2}^{+}$ levels, the precise energy separation of these levels was measured to be 0.44±0.02 keV. On the basis of the observed decay properties, the parity nonconserving matrix element $\left|〈{\frac{17}{2}}^{+}\right|H_{\mathrm{PN}}\left|{\frac{17}{2}}^{-}〉\right|$ was determined to be less than 0.34 eV.

NUCLEAR REACTIONS ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}({}_{}{}^6{}_{}{}^{}\mathrm{Li},3n)$ $E_{\mathrm{Li}}=34\mathrm{}$ MeV pulsed beam; measured $\gamma -\gamma$ coincidence; deduced levels in ${}_{}{}^{93}{}_{}{}^{}\mathrm{Tc}$; measured $\gamma (\theta ,t)$; deduced $T_{\frac{1}{2}}$, $B\left(E2\mathrm{}\right)\mathrm{}$, effective charges, parity mixing. Enriched target, Ge(Li), Si(Li) detectors.

• Received 2 October 1975

DOI:https://doi.org/10.1103/PhysRevC.13.1194