Theoretical characterization of the collective resonance states underlying the xenon giant dipole resonance

We present an ab initio theoretical characterization of the two fundamental collective resonances underlying the xenon giant dipole resonance (GDR). This is achieved consistently by two complementary methods implemented within the many-body configuration-interaction singles (CIS) theory. We identify one resonance at an excitation energy of 74 eV with a lifetime of 27 as, and the second at 107 eV with a lifetime of 11 as. Insights on the nature of these resonances are provided, as well as information on previously unknown resonances in xenon