Barrier distributions from the fusion of oxygen ions with<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Sm</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>1</mml:mn><mml:mn>4</mml:mn><mml:mn>4</mml:mn><mml:mo>,</mml:mo><mml:mn>1</mml:mn><mml:mn>4</mml:mn><mml:mn>8</mml:mn><mml:mo>,</mml:mo><mml:mn>1</mml:mn><mml:mn>5</mml:mn><mml:mn>4</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">W</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>186</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>

Fusion excitation functions for the reactions $^{144,148,154}\mathrm{Sm}$ and $^{186}\mathrm{W}$ + $^{16}\mathrm{O}$ and $^{144}\mathrm{Sm}$ + $^{17}\mathrm{O}$ have been measured with high precision, both in the cross sections and the small energy intervals, thus allowing meaningful fusion barrier distributions to be extracted. In this representation it is clearly seen that the excitation functions are not smooth and featureless; each is unique and is shown to depend on the details of the structure of the interacting nuclei. The effects of excitation of the collective single phonon states in $^{144}\mathrm{Sm}$ are evident. For the $^{17}\mathrm{O}$ projectile, the role of additional coupling to neutron stripping channels with positive Q values can be seen. As expected, the barrier distributions associated with $^{154}\mathrm{Sm}$ and $^{186}\mathrm{W}$ are dominated by deformation effects. However, the data appear to display sensitivity to additional couplings, even though they involve relatively weak inelastic and transfer channels.