Shell Effects at High Angular Momentum

Major-shell effects are seen in the unresolved $\gamma$-ray spectra coming from high-spin states in the transition region: ${}_{}{}^{154}{}_{}{}^{}\mathrm{Er}$ to ${}_{}{}^{160}{}_{}{}^{}\mathrm{Er}$. The angular momentum alignments in the valence shell, which are spread in frequency in the heavier nuclei, are compressed into the low-frequency region in the lighter nuclei and separate almost completely from the angular momentum contributions due to the next higher major (proton) shell.