Contribution of transfer ionization to total electron capture from a helium target

The contribution of transfer ionization (TI) to total electron capture has been measured for ${\mathrm{O}}^{q+}$ ions ($q=5, 6, 7, \mathrm{and} 8$) colliding with helium at energies from 0.5 to 1.5 MeV/u. These measurements, along with other published results, suggest a maximum TI contribution to total capture of $\sim 0.15q^{0.5}$ at $\frac{E(\mathrm{in}\mathrm{keV}/\mathrm{u})}{q^{0.5}}\simeq 100$ The results demonstrate that the failure to account for transfer ionization in total single-charge-transfer cross sections may lead to large discrepancies between experiment and theory.