A drift chamber study of the reaction ArH+H+H2 ->H+ + Ar and related reactions

Abstract

Ion-molecule reactions in argon- hydrogen mixtures were studied as a function of total and partial pressures, using a drift chamber mass spectrometer. The rate coefficient of the title reaction was found to depend on pressure, decreasing as the total pressure is increased from a value of 3.5×10-10 at low pressure to 3.5 X10 cm3 molecule -1s-1 at pressures greater than 0.8 Torr. This behavior is explained by the presence of vibrationally excited ArH+ ions formed in the reaction Ar+ + H2, and their deactivation by collisions with argon atoms. The thermalized ArH+ ions react with hydrogen more slowly than the excited ArH+ ions first formed. Rate coefficients for these processes and for several other ion reactions occurring in argon-hydrogen mixtures are given. © 1981 American Institute of Physics.