Dipole response of Sr88 up to the neutron-separation energy

R. Schwengner, G. Rusev, N. Benouaret, R. Beyer, M. Erhard, E. Grosse, A. R. Junghans, J. Klug, K. Kosev, L. Kostov, C. Nair, N. Nankov, K. D. Schilling, and A. Wagner
Phys. Rev. C 76, 034321 – Published 24 September 2007

Abstract

The dipole response of the magic N=50 nucleus Sr88 was studied in photon-scattering experiments at the electron linear accelerator ELBE with bremsstrahlung produced at kinetic electron energies of 9.0, 13.2, and 16.0 MeV. We identified 160 levels up to an excitation energy of 12 MeV. By using polarized photons linear polarizations of about 50 γ transitions were measured that enabled parity assignments to the corresponding states. In the energy range of 6–12 MeV we identified only one M1 transition; all other transitions have E1 character. Thus, E1 character was proven for 63% of the total dipole strength of the observed levels in the given energy range. Statistical methods were applied to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. In this way we derived the photoabsorption cross section up to the neutron-separation energy. This cross section matches well the photoabsorption cross section obtained from (γ,n) data and thus provides information about the extension of the dipole-strength distribution toward energies below the neutron-separation energy. An enhancement of E1 strength at 6–11 MeV may be considered as an indication for a pygmy dipole resonance.

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  • Received 14 February 2007

DOI:https://doi.org/10.1103/PhysRevC.76.034321

©2007 American Physical Society

Authors & Affiliations

R. Schwengner1, G. Rusev1, N. Benouaret1,2, R. Beyer1, M. Erhard1, E. Grosse1,3, A. R. Junghans1, J. Klug1, K. Kosev1, L. Kostov4, C. Nair1, N. Nankov1,4, K. D. Schilling1, and A. Wagner1

  • 1Institut für Strahlenphysik, Forschungszentrum Dresden-Rossendorf, Postfach 510119, D-01314 Dresden, Germany
  • 2Faculté de physique, Université des Sciences et de la technologie d'Alger, El-Alia 16111, Bab-Ezzouar-Alger, Algerie
  • 3Institut für Kern- und Teilchenphysik, Technische Universität Dresden, D-01062 Dresden, Germany
  • 4Institute for Nuclear Research and Nuclear Energy, BAS, BG-1784 Sofia, Bulgaria

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Issue

Vol. 76, Iss. 3 — September 2007

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