Colloquium on March 31st, 2008

Mahir S. Hussein
Martin Gutzwiller Fellowship, Award Ceremony

Role of Chaos in the Collective Response of Atom Clusters and Nuclei

The excitation of collective states in mesoscopic systems and nuclei is discussed using unifying concepts containing the coherent and chaotic natures of the many-body dynamics. The exit doorway model is employed for the description of the excitation of such resonances. Such a theory allows the inclusion of the width in the dynamical time evolution of the system. It is argued that chaos enters in two disctinct ways. On the one hand, the damping of the plasmon resonances in clusters and giant resonances in nuclei is measured, to a great degree, by the degree of chaoticity of the underlying background many-body states. On the other hand, the same damping allows the dynamical enhancement of the excitation probabilities of multi-phonon resonances. Several examples are presented from Sodium, Potassium and Lithium clusters as well from Oxygen, Calcium, Xenon, Neodymium and Lead nuclei.