Theoretical description of the ejected-electron spectrum in collisions of 1.5-MeV/u F9+ with helium.

Abstract

We present the results of an extensive classical trajectory Monte Carlo (CTMC) simulation of the ejected electron spectrum in collisions of 1.5-MeV/u F[sup 9+] with helium. Excellent agreement is found with the measurements of Lee [ital et] [ital al]. [Phys. Rev. A 41, 4816 (1990)] for ejection to 0[degree]. In particular, the simulation reproduces extremely well the shape and magnitude of the electron-capture-to-the-continuum and binary peaks. We contrast this agreement with calculations utilizing various quantum-mechanical perturbation theories. Also, a continuum-distorted-wave--eikonal-initial-state approach, which describes the interaction between the outgoing electron and the residual target ion through a model potential, has been utilized. This approach is shown to be an improvement over conventional calculations based on the use of effective charges. We draw conclusions regarding the proper representation of the collision dynamics leading to electron ejection in the low-energy, electron-capture-to-the-continuum, and binary peak regimes. Calculations of the doubly differential ionization cross section for non-0[degree] ejection are displayed as well.