Transition probabilities in transitional nuclei in the A=130 region

Lifetimes of excited nuclear states have been measured in 124Ba, 128Ba and 130Ce using the coincidence-plunger technique. The nuclear reactions employed were 100Mo(28Si,4n)124Ba, 114Cd(18O,4n)128Ba and 98Mo(36S,4n)130Ce at beam energies of 115 MeV, 75 MeV and 150 MeV, respectively. The measurements have been performed using the OSIRIS-MIPAD and the OSIRIS spectrometer, as well as the ESSA 30 set-up. It was possible to determine lifetimes in 130Ce for the 4+ to 16+ states and in 128Ba for the 2+ to 8+ states of the ground state band (gsb), the 4+, 6+ and 8+ state of the γ -band as well as for 3 negative parity states. Preliminary results are obtained for 124Ba. The corresponding B(E2) values support the interpretation that 128Ba is a good example of an O(6)-type nucleus. The B(E2) values for 130Ce indicate that the nucleus is less γ-soft than 128Ba. The experimental values could be well reproduced by calculations using the triaxial rotor model with β = 0.26 and γ = 210 as well as the rotation vibration model (β 0.25). (author)