The nucleus 94 Mo was investigated using a powerful combination of γ-singles photon scattering experiments and γγ-coincidence studies following the βdecay of 94m Tc. The data survey short-lived J π = 1 + , 2 + states and include branching ratios, E2/M 1 mixing ratios, lifetimes and transition strengths. The proton-neutron mixed-symmetry (MS) 1 + scissors mode and the 2 + MS state are identified from M 1 strengths. A γ transition between MS states was observed and its rate was measured. Nine M 1 and E2 strengths involving MS states agree with the O(6) limit of the Interacting Boson Model-2 using the proton boson E2 charge as the only free parameter.

No abstract

Abstract. The Miniball germanium detector array has been operational at the REX (Radioactive ion beam EXperiment) post accelerator at the Isotope Separator On-Line facility ISOLDE at CERN since 2001. During the last decade, a series of successful Coulomb excitation and transfer reaction studies have been performed with this array, utilizing the unique and high-quality radioactive ion beams which are available at ISOLDE. In this article, an overview is given of the technical details of the full Miniball setup, including a description of the γ-ray and particle detectors, beam monitoring devices and methods to deal with beam contamination. The specific timing properties of the REX-ISOLDE facility are highlighted to indicate the sensitivity that can be achieved with the full Miniball setup. The article is finalized with a summary of some physics highlights at REX-ISOLDE and the utilization of the Miniball germanium detectors at other facilities.

No abstract

Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A ¼ 42, 46, 50, and 54 "f-shell" nuclei in ( 3 He, t) charge-exchange reactions. In the 42 Ca → 42 Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the 54 Fe → 54 Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.