Proton-neutron structure of low lying collective quadrupole excitations in (126)Xe

Low spin states of the nucleus (126)Xe were studied by means of y-spectroscopy using the fusion evaporation reaction (123)Te(alpha,n)(126)Xe performed at the Cologne FN TANDEM accelerator. The yy coincidence and singles spectra were measured with the osiRls-cube spectrometer. Beside the ground and quasi-gamma bands many other low lying states were observed, yy directional correlations from oriented states (DCO) were analyzed to determine the multipolarities of the gamma-transitions. We observed dominant E2-transitions in the quasi-gamma band and from the gamma- to the ground band but also a large Mi-fraction in the 6^+(2) ->6^+(1) transition. We additionally found a strong M1-decay depopulating the 2^+(4)-state at 2064 keV. The lifetime of this state was measured using the Doppler shift attenuation technique. The experimental data are compared with a calculation using the Proton-Neutron Interacting Boson Model (IBM-2). Good agreement is reached in the vicinity of the O(6)-limit. The observed M1-transition of the 2^+(4) state is interpreted as due to a fragment of the lowest 2^+ mixed-symmetry state predicted by the IBM-2.