The capture of many electrons by Ar !7+ ions, at low velocity, near a metallic surface, has been studied. Multiexcited bound states with many electrons in the outermost shells (hollow atoms) have been observed. The surrounding of an ionic excited core by many outermost electrons greatly decreases the lifetimes of the states. This characteristic decrease explains the main striking features of the relaxation of the ions.

Cross sections for the ionization-excitation of helium following electron and H+, H2+ and H3+ ion impact have been measured for He II (np) 2P0 states with n=2-5. These measurements were performed for the velocity range from 3.8-8.5 au for electrons, 1.4-7.5 au for protons and 1.4-4.0 au for H2+ and H3+ ions. The cross sections have been obtained by measuring the extreme ultraviolet (EUV) emission from the decay of the excited target atoms at 90 degrees to the projectile beam. We have compared our results to the current limited literature for He II (2p) 2P0 cross sections with good agreement observed. We have also examined the cross section ratio of ionization-excitation to excitation, sigma +*((np)2P0)/ sigma *((1snp)1P0), for electron and proton impact in comparison with the ratio of double to single ionization, sigma ++/ sigma +, as a limiting value for large n. Finally, cross section results from Hn+ impact, where n=1-3, are discussed in terms of a semiempirical scaling relation for molecular hydrogen projectiles.

Cross section measurements and calculations are presented for electron capture by multiply charged ions from atomic hydrogen. The measurements were made for Nq+, Oq+ and Neq+ projectiles in the energy range 2 q to 10 q keV. Fair agreement is obtained with most earlier measurements when available. Molecular calculations, including translation factors, have been carried out for the case of fully stripped projectiles with charges between 5 and 10 as well as for O 6+(1s2) and N5+(1s2) impact The role of the interaction between the core and active electron is discussed Good agreement is obtained between theory and experiment. It is worth noting that both experimental and theoretical results do not show any oscillation as a function of the projectile charge in the energy range covered by the experiments