Influence of higher-order deformations in the ³⁴S+¹⁶⁸Er fusion reaction

The shape of the measured barrier distribution for the ³⁴S+¹⁶⁸Er reaction is analyzed using the coupled-channels description. The ¹⁶⁸Er nucleus is a good candidate to test current fusion models description of deformation since it has a large quadrupole deformation with an insignificant hexadecapole deformation. Coupling to weaker channels, the 2₁⁺ state in ³⁴S, the 3₁^- state in ¹⁶⁸Er, and the pair neutron transfer channel, all were found to have little influence on the barrier distribution. A successful description of the barrier distribution was only obtained after the hexacontatetrapole deformation term in ¹⁶⁸Er (β₆^T) was included in the coupling scheme. However, a positive value for β₆^T was needed where the macroscopic-microscopic model predicts a negative one.