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HK: Fachverband Physik der Hadronen und Kerne

HK 5: Struktur und Dynamik von Kernen

HK 5.1: Gruppenbericht

Montag, 4. März 2013, 11:00–11:30, HSZ-301

Dipole response of ⁶⁰Ni below 10 MeV: A new experimental signature for the Pygmy Dipole Resonance — •Marcus Scheck — IKP, TU Darmstadt, Darmstadt, Germany

A campaign of photon-scattering experiments off the semi-magic nucleus ⁶⁰Ni has been performed. The nucleus was investigated using continuous bremstrahlung photons with end-point energies of 6.0, 8.0, and 9.9 MeV and quasi-monochromatic, fully-polarized, Compton-backscattered laser photons in the entrance channel of the (γ, γ^′) reaction. The corresponding measurements were conducted at the DHIPS setup located at the S-DALINAC accelerator in Darmstadt and the photon scattering setup at HIγ^→S facility at TUNL.

The observed experimental quantities, such as for example, angular distribution ratios and scattering cross sections allowed to deduce a detailed picture of photo excited spin-1 states of positive and negative parity. A comparison with the previously studied isotope ⁵⁸Ni reveals the evolution of the E1 Pygmy Dipole Resonance (PDR) in these almost N=Z nuclei. Exploiting the quasi-monochromacy of the Compton-backscattered beams at TUNL a detailed picture of the decay behavior of the photo-excited spin-1 states can be drawn. A change of the integral branching ratios, together with the distribution of final levels of those decays to lower-lying levels with excitation energy is interpreted as a new signature for the wave functions of 1⁻ levels to be dominated either by PDR or Giant Dipole Resonance components. Funding by the DFG within the SFB634 is gratefully acknowledged.