E2 transition probabilities in the decoupled band of the 129La nucleus

Lifetimes of the yrast levels with spins I π = 23/2 − to 39/2 − in 129 La produced via the 120 Sn( 14 N, 5 n ) reaction at a beam energy of 77MeV have been measured by the Doppler shift attenuation method. The properties of the studied levels belonging to the πh 11/2 band were compared with the theoretical predictions obtained in the framework of the core quasi-particle coupling model. It is suggested that the rigid-rotor model used to describe the cores is too simplified as the even-even nuclei from the A ∼ 130 region are susceptible to shape deformation. Reasonable agreement was obtained with the phenomenological cores based on the experimental data of 128 Ba.