Resonant Electron Capture and Stripping in Moderately Large-Angle Atomic Collisions

Differential scattering of ions by atoms in the energy range of 1 kev to 200 kev has been studied. The incident ion, after a single collision which is hard enough to result in a 5° deflection, was analyzed to determine whether it had captured or lost electrons. The angle 5° was chosen as a typical moderately large angle and held fixed as the energy of the incident ion was varied. When the electron capture probability is plotted vs energy, one or more peaks are observed. For the symmetrical case of ${\mathrm{He}}^{+}$ on He, seven peaks are clearly outlined. Four peaks appear in the ${\mathrm{H}}^{+}$ on He combination and three with ${\mathrm{H}}^{+}$ on ${\mathrm{H}}_2$. Single or double peaks are found in other cases studied which include ${\mathrm{H}}^{+}$ on ${\mathrm{N}}_2$, ${\mathrm{O}}_2$, air, Ne, Ar, and Kr; ${\mathrm{H}}_2^{+}$ on ${\mathrm{H}}_2$ and He; ${\mathrm{H}}_3^{+}$ on ${\mathrm{H}}_2$ and He; ${\mathrm{He}}^{+}$ on ${\mathrm{H}}_2$, Ne, Ar, and Kr; ${\mathrm{N}}^{+}$ on Ar; ${\mathrm{N}}_2^{+}$ on ${\mathrm{N}}_2$; ${\mathrm{Ne}}^{+}$ on Ne and Ar; ${\mathrm{Ne}}^{++}$ on Ne and Ar; ${\mathrm{Ar}}^{+}$ on Ar; and ${\mathrm{Kr}}^{+}$ on Kr. For each case the probabilities for electron capture, scattering without change of charge, and various degrees of electron stripping are plotted vs energy. In those cases in which the electron capture probability curve has more than two peaks, these peaks are nearly evenly spaced when the probabilities are plotted vs the time of the interaction. This indicates an electron exchange effect whose period is of the order of ${10}^{-16\mathrm{}}$ second. In cases where there are many electrons involved in the colliding atoms the phenomenon is more complicated, but vestiges of this resonant exchange are sometimes observed.