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Splitting of the pygmy dipole resonance in 138Ba and 140Ce observed in the (α,α γ ) reaction

J. Endres 1 D. Savran 2, 3 A.M. van den Berg 3 P. Dendooven 3 M. Fritzsche 2 M.N. Harakeh 3, 4 J. Hasper 1 H.J. Wörtche 3 A. Zilges 1
1 Institut für Kernphysik der Universität zu Köln
2 Institut für Kernphysik
3 KVI - Kernfysisch Versneller Instituut
4 GANIL - Grand Accélérateur National d'Ions Lourds
Abstract : The N = 82 nuclei 140Ce and 138Ba have been investigated by means of the (α,α γ ) coincidence method to study the pygmy dipole resonance (PDR). The experiments have been performed at the AGOR cyclotron at KVI, Groningen, at a primary beam energy of Eα = 136 MeV. The Big-Bite Spectrometer and seven large-volume high-purity germanium detectors were used in coincidence to perform a simultaneous spectroscopy of the scattered α particles and the γ decay. The comparison with results of nuclear resonance fluorescence experiments reveals a splitting of the PDR into two components. Up to about 6 MeV the same states that could be observed in (γ,γ ) are also excited in α-scattering experiments, whereas the higher-lying states are missing in the (α,α γ ) reaction. This indicates a structural splitting of the PDR into two modes with different underlying structure.
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Contributor : Michel Lion <>
Submitted on : Monday, October 5, 2009 - 9:43:26 AM
Last modification on : Thursday, February 1, 2018 - 1:26:20 AM

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J. Endres, D. Savran, A.M. van den Berg, P. Dendooven, M. Fritzsche, et al.. Splitting of the pygmy dipole resonance in 138Ba and 140Ce observed in the (α,α γ ) reaction. Physical Review C, American Physical Society, 2009, 80, pp.0304302. ⟨10.1103/PhysRevC.80.034302⟩. ⟨in2p3-00421874⟩

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