Measurement of Charge-Exchange Cross Sections for H+, H2+, and He+ Ions

Abstract

Measurements have been made of the charge-exchange cross sections for the ion-molecule pairs: ${\mathrm{H}}^{+}$ + ${\mathrm{H}}_2$, ${\mathrm{H}}_2^{+}$ + ${\mathrm{H}}_2$, ${\mathrm{H}}^{+}$ + Ar, ${\mathrm{H}}_2^{+}$ + Ar, ${\mathrm{H}}^{+}$ + Kr, ${\mathrm{H}}_2^{+}$ + Kr, ${\mathrm{H}}^{+}$ + Xe, ${\mathrm{H}}_2^{+}$ + Xe, ${\mathrm{He}}^{+}$ + Ar, ${\mathrm{He}}^{+}$ + Kr, and ${\mathrm{He}}^{+}$ + Xe in the energy range of 70 to 1050 eV, employing electric fields in a collision chamber to collect slow ion-collision products. The present work generally confirms previous measurements, but shows larger values for low-energy cross sections of Kr and Xe, a systematic discrepancy that can be attributed to the design of the apparatus used in previous work. The present results are consistent with the predictions of the adiabatic theory and with reported observations of optical excitation of the heavy rare gases by low-energy helium-ion charge-exchange processes.