Investigation of the γ-decay behavior of 52Cr with the γ3 setup at HIγS

J Wilhelmy,U Gayer,J Isaak,D Savran,P Ries,W Tornow,B Löher,M Müscher,C Romig,V Werner,M Zweidinger,S.G Pickstone,N Pietralla,P Erbacher,A Zilges,M Spieker

doi:10.1088/1742-6596/966/1/012035

Abstract

The γ-ray strength function is an important input parameter for the calculation of nucleosynthesis processes. To study the dipole response in more detail, the γ-decay behavior of the fp shell nucleus 52Cr was investigated with the high-efficiency γ3 setup at the High Intensity γ-ray Source facility at TUNL in Durham, USA. The highly intense quasi mono-energetic γ-ray beam allows for excitations selective in multipolarity (J=1 and J=2) and energy. The γ3 setup is a multi-detector array consisting of HPGe and LaBr3 detectors with high efficiency and enables the measurement of γ-γ coincidences. Experimental results of 52Cr will be presented and discussed in this contribution.

Highlights

The γ-ray strength function (SF) is an important input parameter for theoretical calculations of nucleosynthesis processes under extreme conditions, e.g., supernovae explosions or binary star mergers
The High Intensity Gamma-ray Source At the High Intensity Gamma-ray Source (HIγS), almost fully polarized γ-ray beams are generated by Laser Compton backscattering (LCB) inside the Free-electron Laser (FEL) optical cavity [26]
E1-strength distribution For 52Cr, seven weaker E1 transitions and 14 γ-decay branching ratios to the first excited states could be observed in this experiment for the first time

Summary

Introduction

The γ-ray strength function (SF) is an important input parameter for theoretical calculations of nucleosynthesis processes under extreme conditions, e.g., supernovae explosions or binary star mergers. At around 5 to 8 MeV, additional E1 strength on top of the lowenergy tail of the IVGDR is observed in nuclei with excess neutrons [12] This resonance-like structure, denoted as Pygmy Dipole Resonance (PDR), is studied with various probes [12]. LaBr3 detectors and HPGe detectors with high energy resolution can be combined depending on the demands of an individual experiment [28]. Four LaBr3 detectors were combined with four HPGe detectors to take advantage of both, high efficiency and high energy resolution. Two HPGe detectors and two LaBr3 detectors were placed at Θ = 90◦ with respect to the beam axis This allows a direct measurement of parity quantum numbers, because of the angular distribution of the E1 and M1 transitions. Two HPGe and two LaBr detectors were placed under backward angles

Parity quantum numbers

Findings

Discussion