Two-quasiparticle and collective excitations in transitional 108,110Pd nuclei.

High-spin states in ^108,110Pd isotopes are studied by γ-ray spectroscopy of heavy-ion-induced fission. The Pd isotopes are produced in the fission channel of the ³¹P + ¹⁷⁶Yb reaction at beam energy 152 MeV. The prompt γ-rays are detected with the EUROBALL4 multidetector array. The yrast states of ^108,110Pd have been observed above the region of the first backbend. The level scheme of ¹⁰⁸Pd was extended with a new negative-parity band. The yrast sequence in ¹¹⁰Pd is observed up to spin I = 14⁺ and negative-parity bands have also been identified. The back bending in these even-mass Pd isotopes is associated with the alignment of the neutron (h_11/2)² pair. The negative-parity states arise from two neutron configurations vh_11/2 ⊗ vg_7/2 and vh_11/2 ⊗ vd_5/2 and they are interpreted in the frame of two-quasiparticle + rotor model as semidecoupled bands. The observed experimental staggering in the γ-bands of ^108,110Pd supports the theoretical predictions for γ-instability of their shapes. [ABSTRACT FROM AUTHOR]