Bochum 2009 – scientific programme
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HK: Fachverband Hadronen und Kerne
HK 71: Nuclear Structure and Dynamics I
HK 71.2: Group Report
Thursday, March 19, 2009, 17:00–17:30, H-ZO 40
Systematic studies of the Pygmy Dipole Resonance by means of the (α,α ′ γ) reaction* — •Janis Endres1, Peter Butler2, Muhsin N. Harakeh3, Rolf-Dietmar Herzberg2, Reiner Krücken4, Norbert Pietralla5, Lucia Popescu6, Deniz Savran5, Marcus Scheck2, Felix Siebenhühner5, Kerstin Sonnabend5, Sotirios Harissopulos7, Anastasios Lagoyannis7, Heinrich Wörtche3, and Andreas Zilges1 — 1IKP, Universität zu Köln — 2Department of Physics, Liverpool, England — 3KVI, University of Groningen, The Netherlands — 4Physik-Department E12, TU München — 5IKP, TU Darmstadt — 6SCK-CEN, Mol, Belgium — 7I.N.P. NCSR Demokritos, Athen, Greece
In the last years investigations have been made to study the electric Pygmy Dipole Resonance (PDR), mainly in semi-magic nuclei. Therefore (γ,γ′) photon scattering experiments have been performed systematically [1]. In (α,α′ γ) coincidence experiments at Eα=136 MeV a comparable energy resolution and a high selectivity of E1 transitions can be obtained by using the Big-Byte Spectrometer at KVI [2]. We give an overview about systematic studies on the nuclei 140Ce, 138Ba, 124Sn and 94Mo. In comparison to the (γ,γ′) reaction a structural splitting of the PDR could be observed which is possibly connected to the different isospin natures of the two groups. There is a low energy part which can be found in (α,α′ γ) as well as in (γ,γ′) reactions and a high energy part which can only be observed in (γ,γ′). * Supported by EURONS and the DFG (SFB 634). [1] U. Kneissl et al., J. Phys. G 32 (2006) R1 [2] D. Savran et al., Phys. Rev. Lett. 97 (2006) 172502