^{109}Pd: Difficulties in particle-rotor models for unique-parity states and revision of spectroscopic factors

Primary and secondary ..gamma.. rays following thermal and p-wave resonant (2.96 eV) neutron capture on /sup 108/Pd were measured to study ..gamma..-ray transitions in /sup 109/Pd. Average resonance capture spectra at 2 and 24 keV were also recorded and the /sup 108/Pd(n,..gamma..ce) reaction was studied and transition multipolarities were deduced. A detailed level scheme up to approx. 1400 keV has been constructed. Numerous spin assignments have been revised, leading to substantial changes in the (d,p) and (d,t) spectroscopic factors, in particular for the g/sub 7/2/ orbit. The data on primary transition intensities for the 2.96 eV resonance are compared with the valence neutron capture model. The level scheme deduced for /sup 109/Pd sheds new light on the previously proposed g/sub 7/2/-h/sub 11/2/ anomaly in the filling of these orbits, suggesting that, at least in /sup 109/Pd, the appearance of the anomaly was largely due to spin misassignments. The revised systematics in the occupation of shell model orbits for a number of nuclei in this mass region is reviewed. Within the level scheme is a group of low-spin negative-parity levels which belong to the same family as the high-spin, decoupled, unique-parity states known in other odd mass Pd isotopes. These statesmore » correspond to the favored and unfavored anti-aligned levels for core rotations R < or = 6. Calculations in the framework of the particle-rotor model cannot reproduce these level energies.« less