The nature of 0+ excitations in 166Er

Lifetimes of excited 0+ states in 166Er have been measured with the (n,n′γ) reaction. The first and second excited 0+ states have no significant collective enhancements of their decays, and their properties are suggestive of pair-type excitations rather than those of a β vibration or phonon excitation built on the γ vibration. The third excited 0+ state at 1934 keV has an enhanced decay to the ground state band with B(E2; 04+ → 2gsb+) = 8.8 ± 0.9 W.u., consistent with that expected for a β vibration.