Coulomb excitation and nuclear deformation
Coulomb excitation is the most direct method to study nuclear collectivity and shapes. In the scattering of two nuclei, the electromagnetic field that acts between them causes their excitation. The process selectively populates low-lying collective states and is therefore ideally suited to study nuclear collectivity. If the distance of closest approach between the projectile and the target is sufficiently large, the short-range nuclear interaction can be neglected and the excitation process can be precisely described using the well-known electromagnetic interaction. In consequence, the measured cross sections to populate excited states in a Coulomb excitation experiment can be directly related to the static and dynamic moments of the charge distribution of the studied nucleus.
The technique has seen a renaissance recently, when Coulomb excitation of unstable nuclei became feasible with use of beams of short-lived exotic nuclei delivered by radioactive beam facilities. However, because of low intensities of post-accelerated beams these studies are often limited to lowest excited states and do not yet reach the level of precision and complexity that one can obtain in stable beam Coulomb excitation experiments. In the seminar I will discuss the observables that can be measured in a Coulex experiment, possible experimental approaches and data analysis techniques, and some recent examples of complex Coulomb excitation studies that will demonstrate how this method can be used to investigate phenomena such as shape coexistence and superdeformation.