Rotational states have been populated in y-soft " Ba following the ' Sn("C,3ny) reaction. The ground state of this nucleus is predicted to possess maximal triaxiality y --30 . Two hI =2 bands were established, based on quasineutron configurations with large negative y deformations close to the collective oblate shape y= -60'. The bandhead of one of these bands, associated with a [vh»z~] configuration, was found to be isomeric with a mean lifetime &=12. 5+0.3 ns. A third EI=2 band was observed, built on a two-quasiproton configuration with a near-prolate shape (y -0 ). In addition, two AI = 1 bands, built on mixed proton-neutron four-quasiparticle configurations with oblate shapes (y --60 ), were established.

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New Nilsson (v, p) parameter sets for the proton X =4, 5, and 6 harmonic oscillator shells are deduced for the A =120-140 mass region by fitting a potential-energy-surface calculation, using the Nilsson-Strutinsky method, to 28 experimental bandhead energies. The results from both the standard and the fitted Nilsson (~,p) parameter sets are compared with experimental bandhead energies. The fitted (a,p) parameter sets achieve a significant improvement in the bandhead energies over this region. In addition, calculated single-particle levels using both the Woods-Saxon and the Nilsson potentials are compared.Considerable experimental and theoretical interest has developed over a period of time in regard to the influence of rotation towards nuclear structure, pairing correlations and shapes of nuclei including the interplay among them. In this regard, the modified harmonic-oscillator potential introduced by Nilsson et al. ' has been extensively employed in the interpolation of deformed nuclei. There are two shell model parameters,~and p, which appear in the potential V= tcfico [21 -s+p(1, -(1, ) )], where~o is the harmonic-oscillator parameter which incorporates the principle of volume conservation for nuclei deformed from spherical shapes. The intrinsic nucleon spin is represented by s, while I, represents the orbital angular momentum in the stretched coordinate basis.The approach of Nilsson et al. ' was to find a given (n', p) parameter pair for the deformed potential that reproduced the experimental level scheme for the extensively studied nuclei of the deformed rare-earth region (A =165) and another (tc, p) pair for those nuclei in the strongly deformed actinide region (A =240). For other regions where only limited experimental data were available at the time, the appropriate (tc, p) pair was formed by extrapolations from the above sets of parameters assuming linear dependences on the mass number A. Better fits to the experimental results for such extrapolated regions were obtained by Bengtsson and Ragnarsson ' using a (tc, p) dependence related to the main oscillator quantum number N, rather than A. Although the resulting so-called "standard set" of (tc, p) values for each oscillator shell are better in the extrapolated mass regions, improvements could still be made in the (tc, p) parameter set by searching for the best theoretical fit to experimental bandhead energies, as was done in the Au-Pt region.Recent interest in the deformed 3 = 130 mass region has developed in regard to the collective and quasiparticle-structure properties as a function of rotational frequency. An extensive set of spectroscopic information has resulted in the availability of systematic bandhead energies over the region 53~Z~63 and 64~N~80. These data on the relative positions of bands built on the gj/2 g9/2 and h»/2 proton Nilsson orbitals allow the extraction of an improved (tc, p) set for protons in the N=4, 5, and 6 oscillator shells from theoretical fits in the A =130 region. Since the N=5 and 6 neutron oscillator shells, and to s...