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

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The shape of the measured barrier distribution for the ³⁴S + ¹⁶⁸Er reaction is analysed 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 2+₁ state in ³⁴S, the 3-₁ 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 (beta₆) was included in the coupling scheme. However, a positive value for beta₆ was needed where the macroscopic-microscopic model predicts a negative one.