Study of high-spin states in 150 Eu and 151 Eu

Abstract High-spin states in 150,151 Eu were populated by the 136 Xe( 19 F, x n) 155− x n Eu reaction. Extensive eγ-, γγ-measurements led to new level schemes of 150,151 Eu. Most observed excitations are interpreted as quasi-rotational bands built on top of multi-p-h states. Enhanced E1 decays competing with E2 transitions indicate an octupole instability of these nuclei at medium spin. Furthermore, a few negative parity bands of 151 Eu decay through large M1 interband transitions which are interpreted as rotations of a triaxial shape. The observed structures at high spin, especially for 151 Eu, show the coexistence of axial and non-axial symmetric shapes.