Speaker
Description
Collective dynamics in atomic nuclei emerge from the coherent motion of many nucleons and provide important insight into how nuclei respond to external perturbations. Resonant photon scattering, or nuclear resonance fluorescence, provides a clean and selective experimental probe of this response. Since real photons couple directly to nuclear charge and current distributions, they can excite and resolve electric and magnetic dipole modes with minimal distortion from the interaction mechanism. This talk will present recent resonant photon-scattering studies performed with quasi-monochromatic, highly polarized photon beams at the High Intensity Gamma-ray Source (HIγS) at the Triangle Universities Nuclear Laboratory. Emphasis will be placed on the use of high-resolution photon scattering to map dipole-strength distributions, identify fine structure and multipole character through polarization asymmetries and angular distributions, and extract reduced transition probabilities as well as photon-strength functions. These observables provide sensitive tests of the microscopic structure of dipole excitations, including strength fragmentation and the emergence of low-energy collectivity. The results will be confronted with state-of-the-art theoretical calculations and compared with complementary data from hadron-induced reactions. These comparisons highlight the distinct selectivity of photon beams and contribute to the interpretation of collective modes relevant to nuclear structure, reaction theory, and astrophysical applications.