The Exchange of Charge between Ions and Atoms

Charge-exchange cross-sections have been measured for ions of between 25 and 900 eV energy in collision with neutral atoms. The method involves collection and measurement of the chargeexchange ions when a beam is passed through gas. The cases A+ in A, He+ in He are in satisfactory agreement with the measurements of Rostagni, although showing no maxima at low energies. The cases O+ in N2, O+ in A, and N+ in A show abnormally high values which are believed to be due to the presence of m etastable ions, as well as contributions from the nitrogen rotational and vibrational energy. The cases H+ in A, in Kr, in Xe and C+ in Xe rise with an increasing energy, to a maximum when aΔE/hv ≏ 1, ΔE being the energy defect of the hv process, v the velocity of the incident ion, and a a parameter of atomic dimensions ~ (5 to 10) 10-8 cm.