Seminarium Fizyki Jądra Atomowego

Understanding how atomic nuclei respond to electromagnetic perturbations provides key insights into their structure and dynamics. In this talk, I will introduce the concept of nuclear response functions, focusing on the electric dipole (E1) mode, one of the most fundamental collective excitations in nuclei. After a brief overview of the main types of nuclear modes (isoscalar vs. isovector, collective vs. single-particle), I will present how these can be theoretically described within the Configuration Interaction Shell Model (CI-SM) framework.
Using the CI-SM, we have systematically computed the E1 strength distributions for all long-lived nuclei in the sd- and p-shell regions. These calculations allow a detailed comparison with predictions from the Quasiparticle Random Phase Approximation (QRPA) and available photoabsorption data. Particular attention will be given to the Pygmy Dipole Resonance (PDR), a low-energy mode that reflects subtle aspects of neutron–proton dynamics. I will discuss how the structure and evolution of the PDR along the Neon and Oxygen isotopic chains shed light on its collectiveness and its classical interpretation as a neutron-skin oscillation mode.