Dissertation / PhD Thesis

GSI-2014-01533

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Probing the decay characteristics of the Pygmy Dipole Resonance in the semi-magic nucleus $^{140}Ce$ with $\gamma$-$\gamma$ coincidence measurements

Löher, B.GSI*

2014

Please use a persistent id in citations: urn:nbn:de:hebis:77-38195

Abstract: This work presents the design and installation of a novel experimental setup -- the $\gamma^3$ setup -- for measuring photon-induced nuclear dipole excitations in stable isotopes at the High Intensity $\gamma$-ray Source (HIγS) at the Duke University. The high energy resolution and high detection efficiency of the detector array, consisting of a combination of LaBr and HPGe detectors, allows for the first time the efficient measurement of $\gamma$³-$\gamma$³-coincidences in combination with the method of nuclear resonance fluorescence. This technique provides access to the decay pattern of dipole excited states as an additional observable, which allows a deeper insight into the underlying structure of these excitations. The experimental setup has already been used successfully for two experimental campaigns in 2012 and 2013 in the investigation of 13 different target isotopes. Within the scope of this thesis the Pygmy Dipole Resonance (PDR) of 140Ce was studied in the excitation energy range from 5.2 MeV to 8.3 MeV based on data obtained with the $\gamma$3 setup. In particular the decay pattern of the states participating in the PDR was investigated. The experimental setup, the details of the analysis and the experimental results are presented in this thesis. A comparison of the results to theoretical quasi-particle phonon model (QPM) calculations allows for an interpretation of the observed decay behaviour.

Keyword(s): Dissertation

Note: Dissertation, Johannes Gutenberg-Universität Mainz, 2014

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Contributing Institute(s):

1. ExtreMe Matter Institute (EMMI) (EXM)
2. Kernreaktionen (KRA)

Research Program(s):

1. 533 - Exotic Nuclei and Nuclear Astrophysics (ENNA) (POF2-533) (POF2-533)
2. EMMI - Helmholtz-Allianz 'Kosmische Materie im Labor', Extreme Matter Institute (HGF-IVF-HA-216) (HGF-IVF-HA-216)

Appears in the scientific report 2014

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