Collisions, involving charge transfer and charge rearrangement, between some of the positive ions and neutral molecules present in the earth's upper atmosphere have been investigated in a crossed beam experiment at energies within the range 2 to 200 ev. The charged reaction products are identified in a mass spectrometer, and absolute cross sections for their production are obtained. Interpolation between these values and those obtained at thermal energy in afterglow experiments provides information on the variation of the cross sections with energy in the intervening energy interval. The influence of excited ions is examined in some detail.

The proton transfer reactions H2+ + He→HeH++H and HeH+ + H→H2++He have been studied in the laboratory energy range 1–25 eV. The first process, which is endothermic for ground state reactants, has been studied over the indicated energy range with different degrees of vibrational excitation present in the H2+ particles. Below 9 eV, the reaction is found to depend strongly on vibrational energy while above this energy the reaction cross sections appear to depend mainly on the kinetic energy of the reactants. The exothermic reverse reaction exhibits a 1 / ν dependence in the low-energy region indicating an ion-dipole mechanism. Methods of measuring the degree of dissociation obtained in forming the hydrogen atom beam are discussed.

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Cross sections for reactions of atomic. oxygen with the ions H+, 0+ ,N " ,Nt, 0-, and 0, have been measured. The ion energies range from 1 to 500 eV. For all ions, the charge transfer processes have been considered. In addition, for Nt the ion-molecule reaction leading to production of NO+ has been studied. For the charge transfer reactions in which no accidentally resonant pathway exists, cross sections less than 10-17 cm' at 1 eV were measured. Where accidental resonance occurs, cross sections larger than 10-16 cm' at 1 eV were found. For N+, both the ground and excited states of the ion were used in the measurements. The method used to form the atomic oxygen beam is discussed.

Laboratory measurements indicate that the metastable ions of O+ in reaction with N2 in the low-energy range (14 eV) react to form principally N2+, while the ion—molecule reaction to form NO+ has a very small probability. The ground-state O+ ion reacts mainly to form NO+. The abundance of metastable O+ 2D ions was determined using the observation that O+(2D)+N2 has a small cross section for forming NO+. The ion energy dependence for both reactions has been measured within the energy range 1.0–500 eV.