Possible Quenching Of Static Neutron Pairing Near The N=98 Deformed Shell Gap: Rotational Structures In Gd-160,Gd-161

A Gd-160 beam was accelerated to an energy of 1000 MeV and, separately, bombarded thick targets of Sm-154 and Dy-164 in order to observe neutron-rich, rare-earth nuclei via deep-inelastic collision processes. Gammasphere was utilized to observe gamma-ray emissions. Many new states and transitions were observed in Gd-160 as a result of so-called unsafe Coulomb excitation. The ground-state band in Gd-160 has been extended to I-pi= 20(+) and a rotational band based on the K-pi = 4(+) state, previously associated with a hexadecapole vibration, was observed up to 18(+). The quasiparticle configuration of the K-pi = 4(+) band has been determined, and its unusual alignment behavior may result from a possible quenching of static neutron pairing. In addition, the band based on the [523]5/2 quasineutron orbital in Gd-161 was extended from 11/2(-) to 33/2(-) and also displays the same unusual alignment behavior.