Experimental Exploration of the Limits of the Nilsson Model; Vibrational States inHf177andHf181

Lack of specific Nilsson states with low $K$ value for assignment of rotational bands observed in ${\mathrm{Hf}}^{177}$ and ${\mathrm{Hf}}^{181}$ between 1 and 2 MeV, together with cross-section measurements, suggest fragmentation of bands into a large number of vibrational components. It is suggested that the previously unobserved pairing vibrations, the $\beta$ vibrations, and the more common $K-2\mathrm{}$ gamma vibrations may be responsible.