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HK: Fachverband Physik der Hadronen und Kerne
HK 59: Structure and Dynamics of Nuclei XI
HK 59.8: Talk
Friday, March 22, 2019, 16:00–16:15, HS 14
Valence-shell dependence of the pygmy dipole resonance in chromium isotopes* — •P. C. Ries1, T. Beck1, J. Beller1, M. Bhike2, U. Gayer1, J. Isaal1, Fnu Krishichayan2, B. Löher1, L. Mertes1, H. Pai3, N. Pietralla1, C. Romig1, D. Savran4, W. Tornow2, S. Typel1, V. Werner1, and M. Zweidinger1 — 1Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt — 2Triangular Universities Nuclear Laboratory, Duke University Durham, NC 27708, U.S.A. — 3Saha Institute of Nulcear Physics, Kolkata 700064, India — 4GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt
The low-lying dipole strength distributions isotopes 50, 54Cr were studied via nuclear resonance fluorescence. Excitation strengths, parity and spin quantum numbers up to 9.7 MeV excitation energy were measured at the superconducting Darmstadt electron linear accelerator S-DALINAC and at the High Intensity γ-ray Source HIγS. In total, 55 states have been observed, 44 of those for the first time. These findings allow the first comparison of electric dipole strengths across a neutron shell closure. The experiments show an increase of E1 transition strength in the energy region of the so-called pygmy dipole resonance as a function of valence neutrons. Calculations within a relativistic mean-field model provide further indications of an onset of the pygmy dipole resonance below the iron isotopes and insight on the development of the strength within the isotopic chain.
*Supported by the DFG within the CRC 1245