Giant Resonances in the Electron-Impact Ionization of Heavy Atoms and Ions

The first interpretation of giant resonance behavior in the inelastic scattering of electrons from heavy ions is reported for the electron-impact double ionization of ${\mathrm{Cs}}^{+}$. A discussion of the partial-wave potentials and phase shifts leading to this phenomenon is presented along with results of several distorted-wave calculations of the cross section. The theoretical cross sections are in good agreement with the results of a crossed-beam measurement.