Resonances and Threshold Effects
Much of the energy-dependent structure observed in low-energy electron scattering arises from resonances and threshold effects. Resonances are due to nearly bound states of the (N + 1)-electron system of target atom and external electron. In a time-dependent formalism, such a state decays with a finite lifetime if it interacts with states in an electron scattering continuum. The uncertainty principle implies a corresponding energy width. Cross sections in the interacting continuum are modified within the energy range defined by the resonance energy and width.
KeywordsResonance Width Threshold Effect Virtual State Elastic Cross Section External Electron
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