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Electron removal (target ionization and/or projectile electron loss) in neutral–atom collisions is theoretically studied for the impact of H0, He0 and He+ beams on noble gases (He, Ne and Ar). These reactions are investigated theoretically within the Continuum Distorted Wave-Eikonal Initial State model. New features have been included in the theoretical model: (i) a scaled projectile charge depending on its velocity and charge, (ii) a dynamic projectile-effective-charge depending on the momentum transfer, and (iii) a dynamic target-effective-charge depending on the kinematics of the emitted electron. The energy and angular spectra of emitted electrons from the target and from the projectile are calculated and compared with the available experimental data. Also, the influence of each one of the corrections on the resulting spectra will be studied.

We measure double differential cross sections (DDCS) of electrons emitted from CH4 molecules in collisions with 250 keV protons. The projectile ions are obtained from a 400 kV electron cyclotron resonance-based ion accelerator (ECRIA). We study the energy and angular distributions of the electron DDCS. The observed double and single differential and the total cross section are compared with the state-of-the-art continuum distorted wave eikonal initial state (CDW-EIS) model predictions. Two different approaches are used considering the different target descriptions: complete neglect of differential overlap (CNDO) and molecular orbital (MO) approximations. The MO model uses two different scaling parameters (d = 0.7 and 1.0). In the energy distribution of the DDCS, the carbon KLL Auger line is also observed at 240 eV. The single differential cross section (SDCS) and total cross section (TCS) are derived. Both the MO-based CDW-EIS models are in good agreement with the experimental results; however, the CNDO approach overestimates the data.