Cross sections for electron capture and loss. I. H⁺ and H^- impact on H and H₂

The electron-capture cross sections for H⁺ impact on H and H₂ and the electron-loss cross sections for H^- impact on H and H₂ have been measured for projectile energies between 2.0 and 0.063 keV. Relative cross-section values for all these reactions were measured directly, and placed on an absolute scale by adopting a standard value of 6.95×10^-16 cm² for the electron-capture cross section for H⁺+H₂ collisions at 2.0-keV H⁺ energy. A crossed-beam technique was used, and the reaction-product H atoms were measured by a secondary-electron-emission detector. The techniques used to make the measurements are described, and the results are compared with other experimental and theoretical data.