Nuclear levels in ¹⁸⁷W

Levels in ¹⁸⁷W have been studied up to 2.2 MeV with the (d,p) and (n,γ) reactions. The (d,p) studies were performed at deuteron energies of 24 and 28 MeV and at two angles of 30° and 50° by using the high resolution Q3D spectrograph in Munich. Primary and secondary γ-rays and γ-γ coincidences were studied with Ge detectors. The combination of these results with the previously known ones allows us to extend the existing level scheme and refine some of its structure assignments. Most of the low-lying states have been classified in terms of the Nilsson model with the extension of some vibrational degrees of freedom. The possibility for the coexistence of triaxial or oblate shapes in ¹⁸⁷W is observed in the form of anti-aligned states with a bandhead of 9/2^- at 364 keV. The polarization effects towards the triaxial shape produced by the odd neutron in specific Nilsson orbitals have been studied. The calculated polarization energies for some γ-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.