New experimental data on the charge-state (q) evolution fractions F q (D) and equilibrium charge-state fractions Fq∞ are presented when 2.65MeV/u C 2+ , O 3+ , Ne 4+ and Si 5+ projectile ions passed through carbon foils with thickness of D=10–200μg/cm 2 . The equilibrium fractions Fq∞ for Si+C collisions (i.e. for silicon ions colliding with carbon foils) are compared with the data at 4.3 and 6.0MeV/u previously reported, and the observed significant difference is explained by different energy dependencies of the electron-capture and projectile-ionization cross sections. Detailed information about nl-state distribution functions N q (nl) of exit silicon ions is obtained for these three energies by solving linear balance equations for N q (nl) values where n and l are the principal and orbital quantum numbers, respectively, and ∑nlNq(nl)=Fq∞. The collision cross sections and radiative decay rates as the coefficients of these balance equations are calculated for each ion-beam energy.Based upon the present method, it is found that the fractions of excited Si ions after the carbon foil are about 57%, 33% and 15% at energies of 2.65, 4.3 and 6.0MeV/u, respectively, clearly indicating the significant reduction of the excited-ion component with the collision energy increasing. The calculated equilibrium charge-state fractions Fq∞ for Si ions are in good agreement with available experimental data.