Nuclear Resonance Fluorescence off 54Cr: The Onset of the Pygmy Dipole Resonance

21st International School on Nuclear Physics and Applications & International Symposium on Exotic Nuclei

Ries, P.C.^1 ; Beck, T.^1 ; Beller, J.^1 ; Krishichayan^2 ; Gayer, U.^1 ; Isaak, J.^3,4 ; Löher, B.^1,4 ; Mertes, L.^1 ; Pai, H.^1 ; Pietralla, N.^1 ; Romig, C.^1 ; Savran, D.^3,4 ; Schilling, M.^1 ; Tornow, W.^2 ; Werner, V.^1 ; Zweidinger, M.^1

Institut für Kernphysik, TU Darmstadt, Schlossgartenstrae 9, Darmstadt

64289, Germany^1

Triangle Universities Nuclear Laboratory, Duke Univ., P.O. Box 90308, Durham

NC

27708-0308, United States^2

Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strae 1, Frankfurt am Main

60438, Germany^3

GSI Helmholtzzentrum für Schwerionenforschung, Planckstrae 1, Darmstadt

64291, Germany^4

关键词: Electron linear accelerator;    Excitation strengths;    Gamma ray sources;    High intensity;    Magnetic dipole;    Nuclear resonance fluorescences;    Pygmy dipole resonances;    Quantum numbers;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/724/1/012040/pdf
DOI  :  10.1088/1742-6596/724/1/012040

来源: IOP

【 摘 要 】

Low-lying electric and magnetic dipole excitations (E1 and M1) below the neutron separation threshold, particularly the Pygmy Dipole Resonance (PDR), have drawn considerable attention in the last years. So far, mostly moderately heavy nuclei in the mass regions around A = 90 and A = 140 were examined with respect to the PDR. In the present work, the systematics of the PDR have been extended by measuring excitation strengths and parity quantum numbers of J = 1 states in lighter nuclei near A = 50 in order to gather information on the onset of the PDR. The nuclei50,52,54Cr and48,50Ti were examined via bremsstrahlung produced at the DArmstadt Superconducting electron Linear Accelerator (S-DALINAC) with photon energies up to 9.7 MeV with the method of nuclear resonance fluorescence. Numerous excited states were observed, many of which for the first time. The parity quantum numbers of these states have been determined at the High Intensity Gamma-ray Source (HIγS) of the Triangle Universities Nuclear Laboratory in Durham, NC, USA. Informations to the methods and the experimental setups will be provided and the results on54Cr achieved will be discussed with respect to the onset of the PDR.