Resonant Electron-Capture Measurements of CloseHe++—He andHe++—H Collisions

Differential measurements of close single collisions are made for the reaction ${\mathrm{He}}^{++}$+He→He+${\mathrm{He}}^{++}$ in which the probability $P_0$ for double electron exchange is found to be an oscillating function of incident energy. Similar measurements for the reaction ${\mathrm{He}}^{++}$+He→${\mathrm{He}}^{+}$+${\mathrm{He}}^{+}$ show that the probability $P_1$ for exchange of a single electron (plotted versus reciprocal velocity) oscillates at twice the frequency of the $P_0$ oscillations. Close encounters in the one-electron collision ${\mathrm{He}}^{++}$+H→${\mathrm{He}}^{+}$+${\mathrm{He}}^{+}$ are also studied here, and the probability $P_1$ of electron exchange plotted versus energy shows an oscillation of low amplitude. The experiments encompass incident ${\mathrm{He}}^{++}$ energies in the range of 2 to 200 keV and scattering angles between 1.2° and 3.0°. The data are discussed using energy-level diagrams of the He${\mathrm{He}}^{++}$ and He${\mathrm{H}}^{++}$ systems.