Frankfurt 2014 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 10: Struktur und Dynamik von Kernen
HK 10.2: Gruppenbericht
Montag, 17. März 2014, 17:00–17:30, HZ 4
Nuclear deformation and neutron excess as competing effects for the pygmy dipole strength — •Ralph Massarczyk1,2, Ronald Schwengner1, Friedrich Dönau1, and Stefan Frauendorf3 — 1Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany — 2Technische Universität Dresden, 01062 Dresden, Germany — 3University of Notre Dame, Notre Dame, Indiana 46556, USA
The electromagnetic dipole strength below the neutron-separation energy has been studied for the xenon isotopes with mass numbers A = 124, 128, 132, and 134 in nuclear resonance fluorescence experiments using the γELBE bremsstrahlung facility at Helmholtz-Zentrum Dresden-Rossendorf and the HIγS facility at Triangle Universities Nuclear Laboratory Durham. The systematic study gained new information about the influence of the neutron excess as well as of nuclear deformation on the strength in the region of the pygmy dipole resonance. The results are compared with those obtained for the chain of molybdenum isotopes and with predictions of a random-phase approximation in a deformed basis. It turned out that the effect of nuclear deformation plays a minor role compared with the one caused by neutron excess. A global parametrization of the strength in terms of neutron and proton numbers allowed us to derive a formula capable of predicting the summed E1 strengths in the pygmy region for a wide mass range of nuclides.