The commonly held view that fusion excitation functions are featureless and do not provide a good test of models is challenged by high-precision measurements for the reaction ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$${+}^{16}$O. The data yield a well-defined distribution of barrier heights using a recently proposed, novel analysis technique. The measured distribution is that expected from the quadrupole deformation of ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$ and models using significantly different distributions cannot reproduce the measured excitation functions.

• Received 12 June 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.3368