Fig. 1. Geometry of scattering. (a) When an energetic ion P with velocity v and impact parameter d moves toward the target T, their electron clouds start to overlap (green area) when R < R_m. (b) The enveloping curve shows a section of the equipotential surface at a given distance R between P and T. This curve represents the border of the classically accessible region for the electrons. S_t and S_p are the areas of the electron density distribution function separated by the potential saddle point at z₀. V(r) is the potential function between T and P. The probability of electron transfer to P at time t is N_Ω(t) = S_p(t)/[S_t(t) + S_p(t)].

Fig. 2. (a) Charge exchange ΔQ and (b) electronic energy loss ΔE at different impact parameters d, with α = 1, f_T = 10, d_min = 1.00 a.u., and ΔQ_max = 18e⁻.

Fig. 3. (a) Energy loss ΔE of 40 keV Xe^q+ ions in CNM as a function of charge exchange ΔQ. Points and lines represent experimental data²³ and calculated values, respectively. (b) Relation between ΔE and incident charge state Q_in for Q_exit = 2. Open squares represent experimental data²³ and solid squares are calculated from the values in (a).

Fig. 4. Normalized intensities of exit charge states Q_exit for different incident charge states Q_in. Points and lines represent experimental data²³ and calculated values, respectively.

Fig. 5. Comparison of calculated and experimentally measured²⁵ ΔE–ΔQ relations for 40 keV Xe^q+ ions penetrating through a graphene monolayer (when Q_exit = 2). The calculation represented by the pink dots used the same parameters as for the CNM calculation, while for the calculation represented by the blue triangles, d_min was adjusted to 1.35 a.u., which gives better agreement with the experimental values.