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IRTG 2891 Nuclear Photonics - Annual Workshop 2024

29 October 2024 to 1 November 2024
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Probing the Giant Dipole Resonance Using Nuclear Resonance Fluorescence

31 Oct 2024, 10:35
25m

Speaker

J. Kleemann (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany)

Description

The giant dipole resonance (GDR) is one of the most fundamental nuclear excitations and it dominates the dipole response of all nuclei. Since its discovery in the early days of nuclear physics it has consistently attracted a great deal of attention. Its evolution from a single-humped structure in spherical nuclei to a double-humped one in deformed nuclei is considered one of the prime signatures of nuclear deformation. This phenomenon is commonly explained through the geometrical model, which depicts the GDR as an isovector oscillation of the proton against the neutron body. However, the geometrical model also makes strong predictions about the γ-decay behavior of the GDR. Yet, despite decades of research on the GDR, its γ decay, though a key property of the resonance, remains poorly characterized, leaving these predictions largely untested.

To address this long-standing issue, photonuclear experiments on the γ decay of the GDR of the well-deformed nuclide $^{154}$Sm and the spherical $^{140}$Ce were recently conducted at the High Intensity γ-ray source (HIγS). Individual regions of the GDR were selectively excited using intense, linearly-polarized and quasi-monochromatic γ-ray beams provided by HIγS. This enabled an excitation-energy-resolved determination of the GDR's elastic and $2_1^+$ Raman γ-scattering cross sections.

The data obtained from these experiments allow for a novel close experimental assessment of the geometrical model of the GDR, in particular for $^{154}$Sm with its double-humped GDR and respective $K$-quantum-number assignments. The findings establish γ decay of the GDR as an observable sensitive to both the structure of the resonance and the nuclear shape.

This research has been funded by the German state of Hesse's Ministry of Higher Education, Research and the Arts (HMWK) under grant No. LOEWE/2/11/519/03/04.001(0008)/62, by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) -- Project-ID 499256822 -- GRK 2891, by the German Federal Ministry of Education and Research (BMBF) under grant No. 05P21RDEN9, and by the U.S. Department of Energy, Office of Nuclear Physics, under grant Nos. DE-FG02-97ER41041 (UNC) and DE-FG02-97ER41033 (TUNL/Duke).

Primary authors

J. Kleemann (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) N. Pietralla (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) U. Friman-Gayer (Department of Physics, Duke University, Durham, North Carolina 27708-0308, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA) J. Isaak (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) O. Papst (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) K. Prifti (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) V. Werner (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) A. D. Ayangeakaa (Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina 27599-3255, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA) T. Beck (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) G. Colò (Dipartimento di Fisica, Universit\`a degli Studi di Milano and Istituto Nazionale di Fisica Nucleare, Sezione di Milano, 20133 Milano, Italy) M. L. Cortés (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) S. W. Finch (Department of Physics, Duke University, Durham, North Carolina 27708-0308, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA) M. Fulghieri (Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina 27599-3255, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA) D. Gribble (Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina 27599-3255, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA) K. E. Ide (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) X. K.-H. James (Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina 27599-3255, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA) R. V. F. Janssens (Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina 27599-3255, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA) S. R. Johnson (Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina 27599-3255, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA) P. Koseoglou (Technische Universität Darmstadt, Department of Physics, Institute for Nuclear Physics, 64289 Darmstadt, Germany) Krishichayan (Department of Physics, Duke University, Durham, North Carolina 27708-0308, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA) D. Savran (GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany) W. Tornow (Department of Physics, Duke University, Durham, North Carolina 27708-0308, USA and Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA)

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