Measurements of cross sections for the formation of Mg2+ ions by collisions between protons and Mg+

Cross sections for the formation of Mg2+ by collisions between protons and Mg+ have been measured at barycentric energies between 0.98 and 44.5 keV. For energies between 3 and 20 keV the cross section is approximately constant at 7 x 10-16 cm2 although some small structure can be resolved. Below 20 keV there is remarkably close agreement between these measurements and the earlier calculation by Bates et al (Proc. Phys. Soc.; 84:517 (1964)) for the process Mg2+ + H → Mg+ + H+. Evidence is presented to indicate that proton impact ionisation of Mg+ is insignificant below 20 keV and so the measurements are believed to refer almost exclusively to the near-resonant charge exchange between protons and Mg+. (author)