Speaker
Description
The giant dipole resonance (GDR) is one of the most fundamental nuclear excitations and dominates the dipole response of all nuclei. Its evolution from a single-humped structure to a double-humped structure is considered as one of the most direct signatures of collectivity and nuclear deformation. Yet, its $\gamma$-decay behavior, despite being a key property, is still mostly unknown.
Recently, novel data on the $\gamma$-decay of the GDR of the well-deformed nuclide $^{154}$Sm and the spherical nuclide $^{140}$Ce were obtained through photonuclear experiments at the HI$\gamma$S facility. Individual regions of the GDR were selectively excited by HI$\gamma$S' intense, linearly-polarized and quasi-monochromatic $\gamma$-ray beam. This enabled an excitation-energy resolved determination of the GDR's $\gamma$-decay behavior. For $^{154}$Sm in particular, the obtained data allow for a first experimental test of the commonly accepted K-quantum-number assignments to the double-humped GDR observed in deformed nuclei.
This work was supported by the State of Hesse under the grant Nuclear Photonics within the LOEWE program and within the Research Cluster ELEMENTS and by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under award numbers 97ER41041 and DE-FG02-97ER41033.
