Rotational band structures in ¹⁵⁴Gd

The N=90 rare earth nucleus ¹⁵⁴Gd has been studied in the spin regime of I<or=26h(cross) by using the reaction ¹⁵⁰Nd(⁹Be, 5n)¹⁵⁴Gd at 55 MeV. Gamma-gamma coincidence and angular correlation data were obtained using the TESSA2 array. Two positive parity sequences have been extended to 26⁺ and four negative parity structures have each been observed up to spins of I=22-24h(cross). The rotational structures observed in ¹⁵⁴Gd are interpreted within the framework of the cranked shell model (CSM) in terms of quasiparticle excitations. The characteristics of the rotational band sequences and the band crossings that occur are compared with those in neighbouring nuclei and to the predictions of this model. The first, second and third i_13/2 neutron alignments in ¹⁵⁴Gd and the systematics of the neutron alignments in the negative parity rotational bands in the even-even N=90 nuclei are discussed. Evidence for quasiproton excitations at the highest spins is discussed.