Charge Exchange and Dissociation Cross Sections for H+1, H+2, and H+3 Ions of 2- to 50-keV Energy Incident Upon Hydrogen and the Inert Gases
Within the energy range 2 to 50 keV, the cross sections for the single-electron capture by protons, for dissociation of H+2 ions into H+1 and H-1 ions, and for dissociation of H+3 ions into H+2, H+1, and H-1 ions, have been measured in hydrogen, nitrogen, and inert-gas targets. The dissociation cross sections were found to decrease by as much as 30% for changes in the operating conditions of the electrodeless discharge-type ion source. The dissociation cross sections were independent of changes in the oscillator frequency, the rf input power, and the dc ion extraction voltage. Changes in both the source gas pressure and transverse magnetic field cause variations in the mean energy and the energy spread of the positive ions extracted from the source; these variations have been related to the population of the vibrationally excited states of the primary molecular ions. The measured cross-section values are accurate relative to one another within 5%. It is shown that the measurements are not invalidated by effects such as competing capture and loss processes outside the collision cell, beam size, and dissociation-product scattering.