Total Cross Section for Charge Transfer of Noble-Gas IonsN2

Abstract

Absolute measurements are reported here of the total cross section ${\sigma }_{10}$ for charge transfer of ${\mathrm{He}}^{+}$, ${\mathrm{Ne}}^{+}$, ${\mathrm{Ar}}^{+}$, ${\mathrm{Kr}}^{+}$, and ${\mathrm{Xe}}^{+}$ in ${\mathrm{N}}_2$ in the energy range from 10 to 100 keV. These measurements were obtained with ions produced in both an rf ion source and an electron-impact ion source. Differences are observed in the measured cross sections obtained with the different sources, except for ${\mathrm{Ne}}^{+}$. These differences are attributed to metastable ions produced in the rf source. (Note: ${\mathrm{Ne}}^{+}$ has no known metastable states.) The largest difference occurs with ${\mathrm{Xe}}^{+}$ ions, where the ratio of the two measurements is 1.5 at a velocity of 2×${10}^7$ cm/sec. In addition, a peak in the ${\mathrm{Xe}}^{+}$ cross sections obtained with the rf ion source is not present in data taken with the electron-impact source. It is believed that the peak is caused by the near resonant charge transfer which can occur between metastable ${\mathrm{Xe}}^{+}$ and dissociative ionization of ${\mathrm{N}}_2$ or with excitation of $\mathrm{N}_2^{}{}_{}{}^{+}$ to the $C{}_{}{}^2{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ state.