No abstract available

[en] Lifetimes of excited states in ^192,194,196Hg were measured using the Generalized Centroid Difference (GCD) method. Three fusion evaporation reactions were used at the Cologne 10 MV Tandem accelerator: ¹⁸⁴W(¹²C,4n)¹⁹²Hg, ¹⁸⁶W(¹²C,4n)¹⁹⁴Hg and ¹⁹⁷Au(p,2n)¹⁹⁶Hg to populate the states of interest. To observe the γ-rays the HORUS spectrometer was equipped with eight HPGe- and nine LaBr₃(Ce) detectors. Lifetimes of 2₁⁺, 4₁⁺ and negative parity band member states were measured in all three nuclei. The experimental results were compared and discussed in the framework of the Interacting Boson Model (IBM). Two model calculations, i.e. IBM-Configuration Mixing (IBM-CM)and IBM-2 were used to describe the nuclei of interest. The two models calculations describe the properties of the nuclei within the experimental uncertainties.

[en] An experiment using the electronic γ-γ ''fast-timing'' technique was performed at the 10 MV Tandem Van-De-Graaff accelerator of the Institute for Nuclear Physics, Cologne in order to measure lifetimes of the yrast states in "1"7"0Yb. The lifetime of the first 2"+ state was determined using the slope method, which means by fitting an exponential decay to the ''slope'' seen in the energy-gated time-difference spectra. The value of τ=2.201(57) ns is in good agreement with the lifetimes measured using other techniques. The lifetimes of the first 4"+ and the 6"+ states are determined for the first time. They are in the ps range and were measured using the generalized centroid difference method, an extension of the well-known centroid-shift method and developed for fast-timing arrays. The derived reduced transition probabilities B(E2) values are compared with calculations done using the confined beta soft model and show good agreement within the experimental uncertainties.

[en] Lifetimes of excited states in ²¹¹At were measured using the electronic γ-γ fast timing technique. The nucleus of interested was populated in a ²⁰⁸Pb(⁶Li,3n)²¹¹At fusion-evaporation reaction at the the 10 MV Tandem accelerator at the Institute for Nuclear Physics, University of Cologne. The lifetimes of the 17/2₁^-, 23/2₁^- states were determined for the first time. The experimental results are compared to two shell model calculations, one using the modified Kuo-Herling interaction and the other using an empirical interaction for 3 particles in a single j=9/2 shell.

[en] In near-spherical nuclei, the two most fundamental quadrupole-collective excitations can be understood as a mixture of the collective 2⁺ proton and 2⁺ neutron excitations: the fully symmetric 2⁺₁ state and the so-called mixed-symmetric 2⁺₁, ms state. Based on the evolution of these states in the N=80 isotonic chain, it has been suggested that the properties of the mixed-symmetry states are sensitive to the underlying subshell structure. In particular, the observed fragmentation of the 2⁺₁, ms of ¹³⁸Ce has been explained as due to the absence of a mechanism dubbed shell stabilization. In order to examine further the effect of shell stabilization of the MSSs, it is necessary to identify and study the properties of these states in the next heavy N=80 isotones beyond Z=58: ¹⁴⁰Nd and ¹⁴²Sm. This Coulomb excitation experiment was performed at the RIB facility ISOLDE at CERN using the MINIBALL HPGe-array. Preliminary results from the experiment are shown.

[en] ²¹²Po lies just two protons and two neutrons above the doubly magic nucleus ²⁰⁸Pb. However, its structure exhibits interesting features of shell model and cluster model configurations. In April 2016 an experiment was performed at the IKP at the University of Cologne with the goal to determine the lifetime of the 4₁⁺ → 2₁⁺ transition in ²¹²Po. The HORUS setup, equiped with 8 HPGe and 8 LaBr₃(Ce) detectors, was used. The nucleus was populated via the ²⁰⁸Pb(¹²C,⁸Be) reaction at 62 MeV. The data were analysed applying the Generalized Centroid Difference Method (GCD). The status of the analysis is presented.