Transfer Ionization of Helium in Collisions with C^q+ and O^q+ (q =1-3)

Cross-section ratios σ_TI/σ_SC of transfer ionization (TI) to single capture (SC) of C^q+- and O^q+-He (q=1-3) collisions in the energy range of 15--440keV/u (0.8--4.2v_Bohr) are experimentally determined. It is shown that σ_TI/σ_SC strongly depends on the projectile velocity, and there is a maximum for E(keV/u)/q^1/2≈150. Combining the Bohr--Lindhard model and the statistical model, a theoretical estimate is presented, in reasonable agreement with the experimental data when E(keV/u)/q^1/2 >35.