Darmstadt 2016 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 68: Structure and Dynamics of Nuclei XII

HK 68.4: Vortrag

Freitag, 18. März 2016, 15:00–15:15, S1/01 A03

Statistical decay of dipole-excited states of Zr isotopes* — •Udo Gayer¹, Markus Zweidinger¹, Tobias Beck¹, Nathan Cooper², Johann Isaak^3,4, Bastian Löher⁵, Laura Mertes¹, Haridas Pai¹, Norbert Pietralla¹, Philipp Ries¹, Christopher Romig¹, Deniz Savran⁵, Marcus Scheck^6,7, Werner Tornow⁸, and Volker Werner¹ — ¹IKP, TU Darmstadt — ²University of Richmond, Richmond, USA — ³EMMI, GSI, Darmstadt — ⁴FIAS, Frankfurt — ⁵GSI, Darmstadt — ⁶School of Engineering, UWS, Paisley, UK — ⁷SUPA, Glasgow, UK — ⁸Duke University, Durham, USA

Decay properties of electric dipole excitations below the neutron separation threshold of ^92,94,96Zr have been determined in several (γ, γ′) and (γ^→,γ′) experiments at the Darmstadt High Intensity Photon Setup and the High-Intensity Gamma-Ray Source in Durham, USA. The model of statistical decay is used to guide an interpretation of this low-lying dipole strength which is frequently discussed to arise from the low-energy tail of the giant dipole resonance and potentially an additional resonance structure often referred to as the pygmy dipole resonance. The availability of three complete data sets in the Zr isotopic chain allowed for a precise test of these extrapolations to low energies using different models for the level density and the photon strength function. In the talk, data and calculations will be presented and the suitability of photon scattering data for this kind of analysis will be discussed.

*Supported by the DFG under research grant No. SFB 634