Low-lying dipole strength of the open-shell nucleus 94Mo

C. Romig, J. Beller, J. Glorius, J. Isaak, J. H. Kelley, E. Kwan, N. Pietralla, V. Yu. Ponomarev, A. Sauerwein, D. Savran, M. Scheck, L. Schnorrenberger, K. Sonnabend, A. P. Tonchev, W. Tornow, H. R. Weller, A. Zilges, and M. Zweidinger
Phys. Rev. C 88, 044331 – Published 29 October 2013

Abstract

The low-lying dipole strength of the open-shell nucleus 94Mo was studied via the nuclear resonance fluorescence technique up to 8.7 MeV excitation energy at the bremsstrahlung facility at the Superconducting Darmstadt Electron Linear Accelerator (S-DALINAC), and with Compton backscattered photons at the High Intensity γ-ray Source (HIγS) facility. In total, 83 excited states were identified. Exploiting polarized quasi-monoenergetic photons at HIγS, parity quantum numbers were assigned to 41 states excited by dipole transitions. The electric dipole-strength distribution was determined up to 8.7 MeV and compared to microscopic calculations within the quasiparticle phonon model. Calculations and experimental data are in good agreement for the fragmentation, as well as for the integrated strength. The average decay pattern of the excited states was investigated exploiting the HIγS measurements at five energy settings. Mean branching ratios to the ground state and first excited 21+ state were extracted from the measurements with quasi-monoenergetic photons and compared to γ-cascade simulations within the statistical model. The experimentally deduced mean branching ratios exhibit a resonance-like maximum at 6.4 MeV which cannot be reproduced within the statistical model. This indicates a nonstatistical structure in the energy range between 5.5 and 7.5 MeV.

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  • Received 15 August 2013

DOI:https://doi.org/10.1103/PhysRevC.88.044331

©2013 American Physical Society

Authors & Affiliations

C. Romig1,*, J. Beller1, J. Glorius2, J. Isaak3,4, J. H. Kelley5,6, E. Kwan6,7,†, N. Pietralla1, V. Yu. Ponomarev1, A. Sauerwein2, D. Savran3,4, M. Scheck1,8,9, L. Schnorrenberger1, K. Sonnabend2, A. P. Tonchev6,7,‡, W. Tornow6,7, H. R. Weller6,7, A. Zilges10, and M. Zweidinger1

  • 1Institut für Kernphysik, Technische Universität Darmstadt, D-64289 Darmstadt, Germany
  • 2Institut für angewandte Physik, Goethe Universität Frankfurt am Main, D-60438 Frankfurt am Main, Germany
  • 3ExtreMe Matter Institute EMMI and Research Division, GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany
  • 4Frankfurt Institute for Advanced Studies FIAS, D-60438 Frankfurt am Main, Germany
  • 5Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, USA
  • 6Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA
  • 7Department of Physics, Duke University, Durham, North Carolina 27708, USA
  • 8School of Engineering, University of the West of Scotland, Paisley PA1 2BE, United Kingdom
  • 9SUPA, Scottish Universities Physics Alliance, Glasgow G12 8QQ, United Kingdom
  • 10Institut für Kernphysik, Universität zu Köln, D-50937 Köln, Germany

  • *romig@ikp.tu-darmstadt.de
  • Present address: National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
  • Present address: Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA.

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Vol. 88, Iss. 4 — October 2013

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