The nucleus ${}^{168}\mathrm{Y}\mathrm{b},$ and its near neighbors, have been studied at the very highest angular momenta using the full Gammasphere array. The experiment was performed in order to search for evidence for the existence of hyperdeformed states, which have predicted nuclear axis ratios of $\approx$3:1. After exhaustive searching for both discrete and continuum γ rays associated with a hyperdeformed shape, using a wide variety of different analysis techniques, no evidence for the existence of hyperdeformation has been found. This search of unprecedented sensitivity has been carried out with the full Gammasphere, and was performed on arguably the best candidate nucleus. A maximum achievable observational limit of $\approx 0.02\%$ of the ${}^{168}\mathrm{Yb}$ channel has been calculated for this particular experiment, using Monte Carlo simulations of the response of Gammasphere.

• Received 5 May 1997

DOI:https://doi.org/10.1103/PhysRevC.56.2502