Hexadecapole deformation in the wolfram nuclei

The (τ, α) and (d, t) reactions have been used to investigate the positive-parity intrinsic excitations in ^{179, 181, 183, 185}W stemming form the i_{$\text{13}\text{2}$} spherical shell-model state. The $\text{13}\text{2}{}^{\mathrm{+}}$ members of the rotational bands built on each of these orbitals are expected to be populated strongly in neutron-transfer reactions due to the near-unity values of the $\text{C}{}_{\mathrm{j}}\text{=}\text{13}\text{2}$ coefficients. These states were populated in the (τ, α) reaction which favours transfer of high angular momentum. The assignments of l-values were based on the measured ratio of (τ, α) to (d, t) cross sections populating the same state. The Nilsson model, with the inclusion of pairing and Coriolis mixing, was unable to account for the experimental results, namely the observation of all the expected strength localized in only two or four states below 2 MeV of excitation. Much better agreement with experiment was obtained if the extended Nilsson model including a hexadecapole deformation of ε₄ ≈ +0.06 was used as a starting point for a Coriolis-coupling calculation.