In the rare-earth deformed region, shifts from systematic Nilsson ground-state assignments are suggested for '" W, "'Os, and for "'"'Ta. Other proposed changes in the regular ordering of Nilsson ground states in the 71( Z( 77,region far from the P-stability line are discussed. NUCLEAR STRUCTURE i i'i7 Ta 77W Os, deduced ground-state Nilsson assignments.Recently revised nuclear data compilations' ' for odd-mass (171-A -185) nuclei far from the P-stability line have indicated possible variations from the regional systematics of Nilsson groundstate assignments. ' Compilers have noted that the p-decay properties of """'Ta are not characteristic of heavier odd-A. tantalums. Similarly, the l3-decay of '7'W displays properties different from those of neighboring 103-neutron isotones.Furthermore, the band structure built on the '"W ground state implies a deviation from the regional trend of Nilsson ground-state assignments. The sharply different character of isomeric decays of "%' and '"Os isotones can be explained by an inversion of the lowest-lying Nil. sson states. Calculations of Nilsson and co-workers' predict changes in the ordering of isotopic and isotonic ground states as a function of quadrupole (e) and hexadecapole (e,) deformation. The Nilsson model predictions' are found to be in general. agreement with the available experimental data. The relative positions of Nilsson base states assigned to odd-neutron and odd-proton rare-earth nuclei are given in Tables I and II. Although -, ' [512] has been regularly ascribed to 103-neutron ground states (see Table I), a shift to 2 [521] probably occurs for the "'W isotone. A large fraction of the '"W P-decay strength is to low-spin (2, -, ) members of IC= 2 bands in '"Ta. ' A partial level scheme for '"Re (14 m) decay to "'% is proposed in Fig. 1, based on our experimental conversion-electron study. ' About 70/g of the total transition intensity assigned to "'W is accounted for in the ground-state~ [521] configuration up to spin -, '. The intraband placements shown in Fig. 1 are consistent with energy, multipolarity, and intensity balance considerations.The & [521] orbital appears at ground also in "'Hg (N = 103), based on measured 8 and p, values. ' A crossing of orbitals -, ' [521] and -, ' [512] TABLE I. Empirical excitation energies (in keV) of odd-neutron Nilsson base states. Nuclide State [521] y f 512]~2 [ 514) 2 [ 624] i7iEr i73yb i75Hf i77W i83H i7'Vb 177Hf i7'W i 8i Os i85Hg & 198 399 126 0 0 920 559 222 0 0 N =103 0 0 0 (114) N= 105 639 508 430 531 636 348 0 0 0 0+X 265 321-309 Our deduced hindrance factors for n decays of 'i 5Hg (of 1.1 and 1.2) suggest that the same 2 f 521] neutron state is populated in the platinum daughters, probably at ground. is predicted at &=0.2. ' Orbitals -, ' [514] and -, [521] are assigned, respectively, to ground and excited levels of 105neutron nuclei Yb, Hf, and 7 gl, with a decreasing excitation energy (see Table I). The ground state of '"Hg (N=105) has been classified' as 2 [521] from measured spin and magnetic mome...
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