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Decay pattern of the pygmy dipole resonance in 60Ni

M. Scheck, V. Yu. Ponomarev, T. Aumann, J. Beller, M. Fritzsche, J. Isaak, J. H. Kelley, E. Kwan, N. Pietralla, R. Raut, C. Romig, G. Rusev, D. Savran, K. Sonnabend, A. P. Tonchev, W. Tornow, H. R. Weller, and M. Zweidinger
Phys. Rev. C 87, 051304(R) – Published 15 May 2013

Abstract

Spin-1 states in 60Ni were excited with the (γ,γ) reaction, exploiting the High Intensity γ-ray Source at Triangle University Nuclear Laboratory. This facility is capable of providing fully linearly polarized, quasimonochromatic, Compton-backscattered photons in the entrance channel of the reaction. The depopulation of low-lying levels in an energy region far below the incident quasimonochromatic photons allows us to obtain average branching ratios of the excited spin-1 states. Levels within the energy region associated with the PDR showed regular behavior and 75% of their decays are direct ground-state decays. The levels in the energy region above the PDR exhibit a statistical decay behavior to a large number of low-lying excited states and have only 50–60% branches to the ground state. Within the framework of the quasiparticle phonon model this feature can be explained with the number of quasiparticles contributing to the wave functions of the excited spin-1 states. Quasimonochromatic photon beams provide a new method to test the microscopic nature of 1 levels.

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  • Received 4 January 2013

DOI:https://doi.org/10.1103/PhysRevC.87.051304

©2013 American Physical Society

Authors & Affiliations

M. Scheck1,*, V. Yu. Ponomarev1, T. Aumann1, J. Beller1, M. Fritzsche1,†, J. Isaak1,2,3, J. H. Kelley4,5, E. Kwan5,6,‡, N. Pietralla1, R. Raut5,6,§, C. Romig1, G. Rusev5,6,∥, D. Savran2,3, K. Sonnabend3, A. P. Tonchev5,‡, W. Tornow5,6, H. R. Weller5,6, and M. Zweidinger1

  • 1Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany
  • 2ExtreMe Matter Institute EMMI and Research Division GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany
  • 3Institut für Angewandte Physik, Goethe-Universität Frankfurt, D-60438 Frankfurt a.M., Germany
  • 4Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, USA
  • 5Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA
  • 6Department of Physics, Duke University, Durham, North Carolina 27708, USA

  • *mscheck@ikp.tu-darmstadt.de
  • Present address: Areva NP GmbH, D-91052 Erlangen, Germany.
  • Present address: Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA.
  • §Present address: UGC-DAE Consortium for Scientific Research, Kolkata Centre, Kolkata 700098, India.
  • Present address: Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

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Vol. 87, Iss. 5 — May 2013

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