Bonn 2010 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 56: Struktur und Dynamik von Kernen IX
HK 56.8: Vortrag
Donnerstag, 18. März 2010, 18:45–19:00, HG VII
Enhancement of dipole strength below the neutron-separation energy in 139La — A. Makinaga1, G. Rusev2,3, •R. Schwengner2, F. Doenau2, D. Bemmerer2, R. Beyer2, P. Crespo2,4, M. Erhard2,5, A.R. Junghans2, J. Klug2,6, K. Kosev2, C. Nair2,7, K.D. Schilling2, and A. Wagner2 — 1Hokkaido University, Sapporo, 060-0810, Japan — 2Forschungszentrum Dresden-Rossendorf, 01314 Dresden, Germany — 3Duke University and TUNL, Durham, NC 27708, USA — 4University of Coimbra, 3004-516 Coimbra, Portugal — 5INFN, Sezione di Padova, 35131 Padova, Italy — 6Vattenfall Power Consultant, 16216 Stockholm, Sweden — 7Argonne National Laboratory, Argonne, IL 60439, USA
The photoabsorption cross section of 139La was measured up to the neutron-separation energy using bremsstrahlung produced at the electron accelerator ELBE of the Forschungszentrum Dresden-Rossendorf with a beam of 11.5 MeV kinetic energy. To estimate branching ratios of transitions from states in the quasicontinuum, we performed simulations of γ-ray cascades. The photoabsorption cross section deduced from the resulting intensities of the ground-state transitions can be combined with photoneutron cross sections to obtain data in a wide energy range up to the giant dipole resonance (GDR). We observe an enhancement of electric dipole strength relative to a Lorentz-like tail of the GDR that cannot be quantitatively reproduced by current model calculations.