Dynamic shape effect in {sup 126}Ba at low spin

Lifetimes of excited states in {sup 126}Ba have been measured with high precision by means of the GASP spectrometer using the coincidence recoil distance technique. The reaction {sup 100}Mo({sup 30}Si,4{ital n}) {sup 126}Ba at a beam energy of 130 MeV was used. The data were analyzed with the differential decay-curve method (DDCM). The obtained transition quadrupole moments disagree with the predictions of the asymmetric rotor model (ARM), the interacting boson model (IBM), and the general collective model (GCM). They give evidence for a sudden dynamic shape change in {sup 126}Ba between the 4{sup +} and 10{sup +} levels of the ground-state band. {copyright} {ital 1996 The American Physical Society.}