γ-ray spectroscopy of 166Hf::X(5) in N > 90? -: art. no. 024309

Excited states in Hf-166 were populated in the beta(+)/epsilon decay of Ta-166 and studied through off-beam gamma-ray spectroscopy at the Yale moving tape collector. New coincidence data found no support for two previously reported excited 0(+) states and led to a substantially revised level scheme. Similarities between the revised level scheme of Hf-166 and the X(5) critical point symmetry are discussed, and the extent of X(5) behavior in this mass region is explored through the W and Os isotopes. Among X(5) candidates with N>90, good agreement is observed for most energies and interband B(E2) strengths, while all exhibit similar disagreements with other key observables, in particular, yrast B(E2) values and spacing in the excited K = 0(+) sequence.