Isomers of half-lives 2.13±0.06 and 2.20±0.15 h have been identified in ${\mathrm{Ba}}^{129}$. The relative ordering of the isomeric states, which most probably have assignments $\frac{9}{2}-$ and ½+, has not been established. Their energy separation is less than 700 keV. No evidence has been found for an isomeric transition. These data are in qualitative accord with the Kumar-Baranger prediction of oblate-equilibrium nuclear shapes for odd-neutron nuclei in this mass region. However, the weight of evidence strongly suggests that the nuclides thus far studied lie in a collective transitional region of predominantly vibrational rather than rotational character.

• Received 12 July 1965

DOI:https://doi.org/10.1103/PhysRev.141.1097