Sign of the Hexadecapole Moments ofTh232andU238Nuclei

The ambiguity in the sign of the hexadecapole moments of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ and ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$, as determined from $\alpha$-particle Coulomb-excitation experiments, has been resolved by experiments using 145-MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ to multiply Coulomb excite these nuclei up to their ${12}^{+}$ states. Excellent agreement with the experimental results was obtained with predictions from the Winther—de Boer program when positive $M\left(E4\mathrm{}\right)\mathrm{}$ values were used, while significant disagreement was found when the negative $M\left(E4\mathrm{}\right)\mathrm{}$ values were used.