Evidence for a7/2+State inMo93

Abstract

The recent shell-model calculations by Bhatt and Ball and by Auerbach and Talmi concerning the level locations and transition probabilities in ${\mathrm{Mo}}^{93}$ have prompted us to perform an experimental examination of the ${\mathrm{Mo}}^{93}$ level scheme. This level scheme was studied through the decays of ${\mathrm{Mo}}^{93m}\left(7\mathrm{} \mathrm{h}\right)$, ${\mathrm{Tc}}^{93m}\left(44\mathrm{} min\right)$, and ${\mathrm{Tc}}^{93}$(2.8 h). The gamma-ray spectra produced in these decays were examined with a Ge(Li) detector and with Ge(Li)-NaI(Tl) coincidence techniques. A new transition of 114 keV, observed in the decay of ${\mathrm{Mo}}^{93m}$, populates a level in ${\mathrm{Mo}}^{93}$ at (1365±3) keV. A spin-parity $\frac{7}{2}+$ is assigned to this level. The $\gamma$ ray previously reported at 1.5 MeV in the spectrum of ${\mathrm{Tc}}^{93}$(2.8 h) was shown to consist of a doublet at 1.477 and 1.521 MeV, and a new $\gamma$ ray at 2.734 MeV was observed. The absence of transitions of 2030 and 2440 keV, which were previously reported to exist, is also of interest. An interpretation of these results in terms of the shell-model computations is discussed.