Nuclear shapes of highly deformed bands in 171,172Hf and neighboring Hf isotopes

A Gammasphere experiment was carried out to search for triaxial strongly deformed (TSD) structures in Hf-171,Hf-172 and the wobbling mode, a unique signature of nuclei with stable triaxiality. Three strongly deformed bands in Hf-172 and one in Hf-171 were identified through Ca-48(Te-128, xn) reactions. Linking transitions were established for the band in Hf-171 and, consequently, its excitation energies and spins (up to 111/2h) were firmly established. However, none of the Hf-172 sequences were linked to known structures. Experimental evidence of triaxiality was not observed in these bands. The new bands are compared with other known strongly deformed bands in neighboring Hf isotopes. Theoretical investigations within various models have been performed. Cranking calculations with the Ultimate Cranker code suggest that the band in Hf-171 and two previously proposed TSD candidates in Hf-170 and Hf-175 are built on proton (i(13/2)h(9/2)) configurations, associated with near-prolate shapes and deformations enhanced with respect to the normal deformed bands. Cranked relativistic mean-field calculations suggest that band 2 in Hf-175 has most likely a near-prolate superdeformed shape involving the pi i(13/2)circle times nu j(15/2) high-j intruder orbitals. It is quite likely that the bands in Hf-172 are similar in character to this band.