Lifetime measurements of yrast states in {sup 162}Yb and {sup 166}Hf

Lifetime measurements of yrast levels in {sup 162}Yb and {sup 166}Hf were performed using the recoil distance Doppler-shift method in coincidence mode. Excited states in {sup 162}Yb and {sup 166}Hf were populated via the reactions {sup 116}Cd({sup 50}Ti, 4n) and {sup 122}Sn({sup 48}Ti, 4n), respectively. The resulting B(E2) values are compared with the X(5) critical point model predictions and interacting boson approximation (IBA) model calculations. The X(5) model provides a reasonable description of the yrast B(E2) values in {sup 166}Hf, whereas the IBA fails to reproduce the transition strengths from the higher spin levels. In {sup 162}Yb, some transitions agree with the X(5) predictions while others are more consistent with the predictions of the IBA or a deformed symmetric rotor.