Ionic collision processes in mixtures of hydrogen and rare gases

Abstract

Bimolecular reactions which occur in weakly ionized mixtures of (H₂ + He), (H₂ + Ne), (H₂ + Ar), and (H₂ + Kr) have been studied while the ions are contained in the space charge trap generated by the passage of a low energy electron beam through the ion source of a mass spectrometer. For the mixtures (H₂ + He) and (H₂ + Ne) the results observed for the primary ions are in agreement with the results of earlier studies. However the hydride ions, produced by reaction of ${\mathrm{H}}_2^{+}$ with He or Ne, have been found to react with rate coefficients which are about 50 times higher than those reported previously. In (H₂ + Ar) and (H₂ + Kr) mixtures the ${\mathrm{H}}_2^{+}$ ions have been found to react with rate coefficients which are in good agreement with the polarization theory. Ar⁺ ions on collision with H₂ react with only about half the predicted value, and approximately one reactive collision in four leads to the formation of ${\mathrm{H}}_2^{+}$ . Both the ²P_(3/2) and the ²P_(1/2) states of Kr⁺ appear to react with a rate coefficient which is only 10% of the value predicted by the polarization theory. A process has been observed in (Kr + H₂) mixtures which leads to the production of ${\mathrm{H}}_2^{+}$ ions. Evidence is presented to support the contention that this process is the collisional deactivation of a krypton ion in a metastable state.