Köln 2025 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 28: Structure and Dynamics of Nuclei VIII

HK 28.3: Vortrag

Mittwoch, 12. März 2025, 16:30–16:45, HS 2 Physik

Nuclear resonance fluorescence of ²⁴²Pu — •M. Beuschlein¹, J. Birkhan¹, J. Kleemann¹, O. Papst¹, N. Pietralla¹, R. Schwengner², C. A. Ur³, S. Weiß², V. Werner¹, U. Ahmed¹, T. Beck^1,4, I. Brandherm¹, A. Gupta¹, J. Hauf¹, K. E. Ide¹, P. Koseoglou¹, H. Mayr¹, C. M. Nickel¹, K. Prifti¹, T. Stetz¹, and R. Zidarova¹ — ¹IKP, Darmstadt, Germany — ²HZDR, Dresden, Germany — ³ELI-NP, IFIN-HH, Bucharest-Magurele, Romania — ⁴FRIB, East Lansing, MI, USA

The availability of nuclear structure information of transuranium actinides impacts the modeling of stellar nucleosynthesis and supports isotope-selective material inspection via photonuclear reactions. However, available experimental data are scarce. The first nuclear resonance fluorescence (NRF) experiment on ²⁴²Pu was conducted at the S-DALINAC at TU Darmstadt to probe its low-energy dipole response under stringent safety precautions. A PuO₂ sample of 1 g was irradiated by bremsstrahlung up to an endpoint energy of 3.7 MeV. The comparison of NRF spectra to measurements of the sample’s activity and natural background revealed photo-excited dipole states of ²⁴²Pu. Evidence for fragments of the M1 scissors mode and for low-lying E1 excitations was found, based on the assignment of intrinsic projection quantum numbers, K, from measured decay branching ratios. Experimental details, γ-ray spectra, and first results on the most prominent observed transitions in ²⁴²Pu will be presented.

This work is supported by the DFG through the research grant GRK 2891 "Nuclear Photonics" under Project-ID No. 499256822.

Keywords: nuclear resonance fluorescence; dipole response; transuranium actinides; scissors mode; nuclear structure