Wobbling Modes in Ta Nuclei?

Although the existence of asymmetric (or triaxial) shaped nuclei has been predicted for decades, acquiring experimental proof of this shape has been quite challenging. A triaxial nucleus should produce a collective wobbling mode when it is given significant angular momentum. Indeed, evidence of this phenomenon has been observed in a few odd-A Lu nuclei. A neutron shell gap is often cited for the stabilization of this rare shape in Lu. Theoretical calculations suggest triaxiality should also be observed in Hf nuclei; but despite several measurements, no wobbling has been confirmed. Recently, a high- spin, Gammasphere experiment aimed at identifying the wobbling mode in $^{171}$Ta was performed in order to determine whether triaxial nuclei can be observed in the N$\approx$100 region. In addition, $^{169}$Ta was found to be strongly populated. No wobbling was found in either nucleus and conclusions based on these results will be discussed.