The following isomeric transitions have been observed in neutron-deficient rare earth isotopes: ${\mathrm{Tb}}^{156m}$ (5.5 hr) 88.2 kev ($E3\mathrm{}$); ${\mathrm{Ho}}^{160m}$ (5.0 hr) 60.1 kev ($E3\mathrm{}$); ${\mathrm{Er}}^{167m}$ (2.5 sec) 208 kev ($E3\mathrm{}$); ${\mathrm{Er}}^{168m}$ (${10}^{-7\mathrm{}}$ sec); and ${\mathrm{Yb}}^{171m}$ (${\mathrm{T}}_{\mathrm{½}}$?) 75.8 kev ($E3\mathrm{}$). All the $E3\mathrm{}$ transitions may proceed between levels predicted by Mottelson and Nilsson.

• Received 18 February 1957

DOI:https://doi.org/10.1103/PhysRev.106.1232