Speaker
Description
The availability of nuclear structure information on transuranium actinides has a direct impact on the modeling of stellar nucleosynthesis and supports isotope-selective material inspection via photonuclear reactions. However, experimental data in this region are still scarce.
The first nuclear resonance fluorescence (NRF) experiment on $^{242}$Pu was conducted at the S-DALINAC at TU Darmstadt to probe its low-energy dipole response under stringent safety precautions. A $^{242}$PuO$_2$ sample with a mass of $1\,\mathrm{g}$ was irradiated with bremsstrahlung up to an endpoint energy of $3.7\,\mathrm{MeV}$. By comparing NRF spectra with measurements of the sample's activity and the natural background, photo-excited states with spin quantum number $J=1$ of $^{242}$Pu were identified. Based on the assignment of the intrinsic projection quantum number $K$ from measured decay branching ratios, evidence was found for five fragments of the $M1$ scissors mode, as well as for low-lying $E1$ excitations. Experimental details, $\gamma$-ray spectra, and first results on the most prominent transitions observed in $^{242}$Pu will be presented.
This work is supported by the DFG through the research grant GRK 2891 Nuclear Photonics under Project-ID No. 499256822.
