Lifetimes of the yrast states of even Ce isotopes

The lifetime of the yrast states Jsup(π) <= approximately 14+ of the isotopes 130132134Ce, populated in the reactions 118120122Sn(16O,4nγ)130132134Ce at a bombarding energy of 76 MeV, were measured by means of the Doppler-shift recoil distance method. A pronounced reduction of the E2 transition strengths within the yrast sequence, increasing strongly with neutron number, was observed. In all cases, the feeding scheme of the yrast states contains long-lived components (tau → 20 ns), the total intensity of which is again correlated to the neutron number. (Auth.)