Illustration of the estimation of the shape parameters for O⁺. The upper panel shows an M/Q histogram for 1.2 ≤ w_C⁺< 1.3. From the peak’s counts (a box with M/Q₀ ± 1 amu e^-1), a histogram of the energy of the ions when hitting the carbon foil is created (lower left panel). TRIM simulations corresponding to the energy bins are obtained. An artificial M/Q histogram is created from the transmitted energy and angular scattering information (lower right panel). A fit to this histogram yields estimated parameters for the real peak.