Excitation functions for the $0^{+}$, $2^{+}$, and $4^{+}$ states of ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$, ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$, and ${}_{}{}^{186}{}_{}{}^{}\mathrm{W}$ were measured at 140° and 173.5° with incident $\alpha$-particle energies between 12.5 and 19 MeV. Strong destructive nuclear-Coulomb interference effects were observed. A coupled-channels code was developed and the deformation parameters ${{\beta }_2}^N$ and ${{\beta }_4}^N$ of the optical potential were determined and are compared with those of the charge distribution, ${{\beta }_2}^c$ and ${{\beta }_4}^c$.

• Received 10 June 1974

DOI:https://doi.org/10.1103/PhysRevLett.33.383