High-spin octupole correlations in the N = 86, 146Nd and 148Sm nuclei

High-spin states in Nd-146 and Sm-148 have been populated using the C-13 + Xe-136 and Ne-22 + Te-130 compound nucleus reactions. Alternating parity bands built on the ground state are observed to spin I = (19) and I = (27) in Nd-146 and Sm-148 respectively. Analysis of the data done in terms of the reflection-asymmetric mean-field approach suggests that both nuclei become octupole-unstable at medium spins. The observed enhancement of E1 rates supports this prediction. In Sm-148 also a structure with simplex quantum number s = -1 is observed. At medium spins the reflection-asymmetric structures coexist with reflection-symmetric configurations. The decrease of the electric dipole moment observed for the N = 86 isotones between Z = 62 and Z = 64 is explained by the transition from static to dynamical octupole correlations