QUANTAL AND CLASSICAL CORRESPONDENCE OF DOUBLE SCATTERING

Electron emission from atom-atom collisions is analysed within the fra mework of both quantal and classical dynamics. We examine the effect o f explicit electron-electron (e-e) interactions on the ejected electro n spectra in hard collisions involving simultaneous excitation and ion ization in the collision of two structured atoms. A double scattering sequence represented by a second-order Born approximation has been sho wn to give a dominant contribution over the single scattering to proje ctile ionization. A classical simulation confirms the double scatterin g process is analogous to the Thomas two-step capture mechanism. We fi nd good agreement between quantal and classical calculations, showing the convergence of the Born series to second order and the possibility of a classical treatment for e-e interactions in non-perturbative reg imes. We also find that the shape of the ejected electron spectrum is very different from the usually assumed Lorentzian distribution.