NUCLEAR-LEVELS IN W-187

Levels in W-187 have been studied up to 2.2 MeV with the (d, p) and (n , gamma) reactions. The (d, p) studies were performed at deuteron ener gies of 24 and 28 MeV and at two angles of 30 degrees and 50 degrees b y using the high resolution Q3D spectrograph in Munich. Primary and se condary gamma-rays and gamma-gamma coincidences were studied with Ge d etectors. The combination of these results with the previously known o nes allows us to extend the existing level scheme and refine some of i ts structure assignments. Most of the low-lying states have been class ified in terms of the Nilsson model with the extension of some vibrati onal degrees of freedom. The possibility for the coexistence of triaxi al or oblate shapes in W-187 is observed in the form of anti-aligned s tates with a bandhead of 9/2(-) at 364 keV. The polarization effects t owards the triaxial shape produced by the odd neutron in specific Nils son orbitals have been studied. The calculated polarization energies f or some gamma-driving orbitals are comparable with the prolate-oblate energy difference which indicates the possibility of the stabilization of triaxial or oblate shapes in these states. (C) 1997 Elsevier Scien ce B.V.