O(6)-symmetry breaking in the {gamma}-soft nucleus {sup 126}Xe and its evolution in the light stable xenon isotopes

Low-lying collective states in {sup 126}Xe have been investigated via the {sup 12}C({sup 126}Xe,{sup 126}Xe{sup *}) projectile Coulomb excitation reaction at 399 MeV. The {gamma} decays were detected with the Gammasphere array. Coulomb excitation cross sections relative to the 2{sub 1}{sup +} state were obtained. Twenty-two absolute E2 transition strengths have been deduced. An sd- interacting boson model (IBM-1) fit agrees well with the new experimental data. This makes a quantitative test of O(6)-symmetry breaking in {sup 126}Xe possible. The measured absolute B(E2) values indicate a preservation of O(5) symmetry, while the O(6) symmetry is broken. The evolution of O(6)-symmetry breaking and of O(5)-symmetry conservation in the {sup 124,126,128}Xe isotopic chain is discussed.

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