High-resolution study of 0+ and 2+ excitations in 168Er with the (p, t) reaction

Excited states in the deformed nucleus 168Er have been studied with high energy resolution in the (p, t) reaction, with the Munich Q3D spectrograph. A large number of excited 0+ states (25) and 2+ states (64) have been assigned up to 4.0-MeV excitation energy. This allows detailed investigations along two directions of current interest: first, an extension of microscopic model interpretations into the region of medium level density above the pairing gap; second, a first analysis of the statistical fluctuation (order/chaos) properties of pure sequences of levels, in one deformed nucleus. Predictions of two models (the quasiparticle-phonon model and the projected shell model) are compared to the data, and it is concluded that, in both cases, mixing of more configurations is required in the wave functions.