Rotational band structure inN=105 and 107isotones: I. Evidence for the transition to|IRj〉coupling at high spins inW179

Abstract

The ${}_{}{}^{177}{}_{}{}^{}\mathrm{Hf}(\alpha , 2n\gamma )$ and ${}_{}{}^{181}{}_{}{}^{}\mathrm{Ta}(p, 3n\gamma )$ reactions have been employed in a study of the ${}_{}{}^{179}{}_{}{}^{}\mathrm{W}$ rotational band structure. Attention is focused on the unique-parity $\frac{9}{2^{+}}\mathrm{}\left[624\right]\mathrm{}$ band and its highly perturbed rotational structure. The higher-spin members of the even-parity band in ${}_{}{}^{179}{}_{}{}^{}\mathrm{W}$ are not well characterized by a single $K$ quantum number and are better represented in the $|I\mathrm{Rj}〉$ weak-coupling scheme. Limits are placed on the hexadecapole deformation consistent with the rotational band structure in ${}_{}{}^{179}{}_{}{}^{}\mathrm{W}$. The relevance of the even-parity band structure in ${}_{}{}^{179}{}_{}{}^{}\mathrm{W}$ to backbending in neighboring even-$A$ nuclei is discussed.