Nuclear Resonance Fluorescence inIr193

The high-speed-rotor technique has been used to tune some of the $\gamma$ rays accompanying the decay of ${\mathrm{Os}}^{193}$ to the corresponding excited states of ${\mathrm{Ir}}^{193}$. Resonant scattering experiments established that the previously reported 559-keV level in ${\mathrm{Ir}}^{193}$ is a doublet. High-resolution Ge(Li) spectrometry led to a value $\Delta E=1.9\mathrm{}\pm 0.1$ keV for the energy separation of the two components of this doublet, and to a ratio I(557): I(559) = 3.0±0.6 for the intensities of the corresponding ground-state transitions in the ${\mathrm{Os}}^{193}$ decay. From a comparison of resonance scattering and self-absorption results, it was concluded that the 559-keV level was responsible for most of the resonant scattering from the doublet, and that this level exhibited considerable branching to the 139-keV excited state. Assuming spins of $\frac{3}{2}$, ½, and $\frac{5}{2}$ for the 460-, 557-, and 559-keV excited states of ${\mathrm{Ir}}^{193}$, and ground-state branching ratios $\frac{{\Gamma }_0}{\Gamma }$ of 0.48, 0.73, and 0.73, respectively, the following level widths were obtained: ${\Gamma }_{460}=(3.3\mathrm{}\pm 0.6)\times {10}^{-5\mathrm{}}$ eV; ${\Gamma }_{557}<1.8\mathrm{}\times {10}^{-4\mathrm{}}$ eV; ${\Gamma }_{559}=(3.7\mathrm{}\pm 0.8)\times {10}^{-4\mathrm{}}$ eV.