Direct lifetime measurements of Coulomb-excited levels in 152Sm, 160Gd, and 171Yb

The principal purpose of the present work was the experimental realisation of Recoil Distance Doppler Shift (RDDS) lifetime measurements of Coulomb excited levels in nuclei. All measurements were carried out at the Cologne FN Tandem accelerator. In order to fix the reaction kinematics and to separate γ-rays stemming from the backing material, the target material and the stopper, respectively, the Cologne Plunger Device has been equipped with six photodiode cells, manufactured by SILICON SENSORS, which were mounted approximately 1 cm upstream of the target to cover an angular range of 155 -175 . The γ-rays were detected in coincidence with the energy signals of the particle detectors with an EUROBALL CLUSTER detector placed at 0 with respect to the beam axis, and three additional high efficiency germanium detectors at backward angles. The data was carefully analysed, taking into account possible deorientation effects and the feeding problem. (orig.)