states in transitional 156 Dy, 159 Er and 160 Er nuclei have been studied using the GAMMASPHERE and EUROGAM γ -ray spectrometers. The lowest energy positive-parity bands in 156 Dy are found to evolve smoothly towards an oblate shape in contrast to the sudden change observed in the neighbouring 158 Er nucleus. In 159 Er, the decay path of the positive-parity yrast band splits above I π = 85/2 + and favoured multi-particle-hole states are identified in the irregular pattern at 89/2 + and 101/2 + . The yrast structure of 160 Er is found to remain collective up to and beyond 50h with no sign of an apparent termination.

The triaxial strongly deformed (TSD) bands in 167Lu were populated by the 123Sb(48Ca, 4n) reaction with a beam energy of 203 MeV. Gamma rays, requiring five fold or more in prompt coincidence, were detected with the Gammasphere spectrometer. Of particular interests are TSD bands 1 and 2 which have previously been interpreted as zero phonon and one phonon wobbling bands, respectively. Using the Doppler shift attenuation method (DSAM), a preliminary transition quadrupole moment of 6.9+0.3−0.3 eb was extracted for the TSD1 band. Data analysis continues for TSD2 which is considerably more weakly populated.

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T h e levels in neutron-rich odd-A 1071109 Ru nuclei have been investigated by using y-y-and y-y-y-coincidence studies o f the prompt y-rays from the spontaneous fission of 252Cf. T h e ground state bands and the negative parity bands are identified and expanded in both nuclei. Tkiaxial rotor plus particle model calculations indicate the ground state bands originate from v(ds/z + g7/2) quasiparticle configurations and the negative parity bands are from vhll/2 orbital.

Level schemes for the neutron-rich 140q143Ba nuclei have been determined by study of prompt y-rays in spontaneous fission of 252Cf. The level pattern and enhanced E l transitions between R = + and T =bands show reflection asymmetric shapes with simplex quantum number s = $1 in 14'Ba and s = fi in 143Ba, respectively. The octupole deformation stability with spin variation has been discussed.