Electromagnetic moments of the 7+ rotational bandhead in116Sb

The lifetimes of low-lying negative parity yrast levels have been measured in¹³¹La using the recoil distance Doppler shift method. The nuclear reaction employed was¹¹⁶Cd+¹⁹F at a beam energy of 80 MeV. The data were analysed using the differential decay curve method. The E2 transition strengths for negative parity yrast states and the energy spectra are well described by coupling a fermion to a-soft core in the frame of the interacting boson fermion approximation model.We gratefully acknowledge discussions with R.F. Casten. One of us (N.V.Z.) is grateful to Universität zu Köln for its hospitality. This work was supported by the Bundesministerium für Forschung und Technology — Germany under contract 06OK143 and by Institute of Atomic Physics — Romania under contract 62-91-1.