Irradiations of natural ytterbium and enriched ${\mathrm{Yb}}^{176}$ samples were found to produce a new radioactive nuclide, which was assigned to ${\mathrm{Er}}^{173}$. The following radiation characteristics were observed to belong to the decay of ${\mathrm{Er}}^{173}$: half-life 12.0±0.3 min; $\beta$-ray energies 1.8±0.3 and 2.3±0.3 MeV, and relative intensities 30±3 and 70±5, respectively; $\gamma$-ray energies 0.087±0.005, 0.100±0.005, 0.115±0.005, 0.128±0.005, 0.155±0.005, 0.182±0.005, 0.197±0.005, 0.205±0.005, 0.278±0.005, 0.300±0.005, 0.365±0.005, 0.380±0.005, 0.395±0.005, and 0.520±0.005 MeV, and relative intensities 10.3±1.0, 6.7±0.5, 7.0±3.5, 4.0±0.5, 18.4±2.5, 20.0±2.0, 59.5±4.0, 4.0±0.6, 5.0±0.8, 3.0±0.5, 18.5±2.0, 19.5±2.0, 30.0±5.0, and 20.0±3.0, respectively. The cross section for ${\mathrm{Er}}^{173}$ production through ($n, \alpha$) reaction on ${\mathrm{Yb}}^{176}$ was measured to be 0.20±0.05 mb.

• Received 2 August 1967

DOI:https://doi.org/10.1103/PhysRev.166.1173