E3 matrix elements have been determined for transitions between states up to ${\mathit{I}}^{\mathrm{\pi }}$=${13}^{\mathrm{-}}$ in ${}_{}{}^{148}{}_{}{}^{}\mathrm{Nd}$, providing direct evidence for strong octupole collectivity in a rotational band. These values, as well as the corresponding E1 and E2 matrix elements, were obtained from Coulomb excitation data using ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$ and ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ ions, projectile excitation using a ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ target, and from recoil distance lifetime measurements. The results are consistent with collective model predictions for ${}_{}{}^{148}{}_{}{}^{}\mathrm{Nd}$ assuming intrinsic quadrupole and octupole moments of ${\mathit{Q}}_{20}$≊400 e ${\mathrm{fm}}^2$ and ${\mathit{Q}}_{30}$≊1500 e ${\mathrm{fm}}^3$. The E3 strength coupling the negative-parity states to the β band is found to be appreciable.

• Received 15 March 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.1990