Doubly differential spectra of scattered protons in ionization of atomic hydrogen

Abstract

We have measured and calculated doubly differential cross sections for ionization of atomic hydrogen using 75-keV proton impact for fixed projectile energy losses as a function of scattering angle. This collision system represents a pure three-body system and thus offers an accurate test of the theoretical description of the few-body dynamics without any complications presented by electron correlation in many-electron targets. Comparison between experiment and several theoretical models reveals that the projectile-target nucleus interaction is best described by the operator of a second-order term of the transition amplitude. Higher-order contributions in the projectile-electron interaction, on the other hand, are more appropriately accounted for in the final-state wave function.

Manipulating Atomic Fragmentation Processes by Controlling the Projectile Coherence

“…This calculation reproduces the measured DDCS coh very well, but is in poor agreement with the DDCS inc . At the same time, the shape of the angular distribution of the DDCS inc agrees nearly perfectly with the DDCS for atomic hydrogen (DDCS H ) measured earlier [25,26] and which are shown as crosses in Fig. 1.…”

“…1). In this model, which was labeled SBA-C, the projectile is described by a Coulomb wave rather than a plane wave [26,28]. Although this also represents a fully coherent treatment of the projectile, its effect on the DDCS is strongly suppressed, if visible at all, compared to the molecular target.…”

“…The solid curve is a molecular 3-body distorted wave (M3DW) calculation [24], which assumes a completely coherent projectile beam. The dashed curve is a Second Born Approximation with Coulomb waves (SBA-C) calculation for ionization of atomic hydrogen [26,28]. Fig.…”

“…The crosses are data for ionization of atomic hydrogen [25,26]. The solid curve is a molecular 3-body distorted wave (M3DW) calculation [24], which assumes a completely coherent projectile beam.…”

“…The phase difference ϕ between the projectile waves diffracted at the two centers is a function of θ, the molecular orientation δ, and D. In our experiment δ was not determined and the DDCS therefore have to be averaged over all δ. This averaging leads to a damping, but not to a complete elimination of the interference structure [26,28]. The measured ratio R, i.e.…”