Charge exchange between multiply charged ions and atoms

An analysis is made of the capture of electrons by excited states of an ion in collisions of atoms with multiply charged ions ($Z\gtrsim10$). General expressions are obtained for the transition probabilities and cross sections of one-electron charge exchange and allowance is made for the strong coupling of the initial and final states of an atom$+$ion system. The capture cross section of an ion level with a binding energy exceeding the ionization potential of an atom is found to have two separate maxima along the energy scale. The total charge-exchange cross section in the range of energies of relative motion $1-10^5$ eV/nucleon is proportional to $Z^2$, where $Z$ is the ion charge. The results of calculations are in quantitative agreement with the published experimental results. It is shown that the two-electron capture cross section is smaller than the one-electron cross section and that in the $Z\ge10$ range an unstable excited state of an ion decays preferentially by the emission of radiation.