Opposite-Parity Bands In Eu-153

Excited states of Eu-153 were observed using the 150Nd(Li-7, 4n) reaction at a beam energy of 40 MeV. Two rotational bands with levels of spins up to 45/2HBAR were seen; a positive parity band built on the 5/2+ ground state, and a negative parity band built on the 5/2- level at 97.5 keV excitation energy. Transitions were also observed from levels in a band built on a 3/2+ state at 103.2 keV. Several features of the 5/2+/- bands suggest octupole instability or deformation, as may be expected for nuclei in this region. Levels of the same spin but opposite parity are nearly degenerate, and strong electric dipole transitions connect appropriate band members. Other features such as gyromagnetic ratios indicate an interpretation in terms of bands associated with separate orbits in a reflection-symmetric potential.