EXPERIMENTAL-STUDY OF THE ENERGY-DEPENDENCE OF THE REACTION-RATE COEFFICIENTS OF THE REACTION CH3+ WITH N2O AND NH3

The kinetics of the reaction of CH3+ ions with N2O and NH3 has been in vestigated in He and Ar buffers using Selected Ion Flow Drift Tube tec hnique (SIFDT). Both studied reactions proceed with nearly collisional rate at near thermal energies. The rate coefficient of the reaction o f CH3+ with N2O is decreasing more than one order of magnitude (from 1 .2 x 10(-9) cm(3)s(-1) up to 8 x 10(-11)cm(3)s(-1)) With reactant ion/ reactant neutral average centre-of-mass kinetic energy (E-r) increasin g from near thermal up to 2 eV. The dominant product of this reaction is the isomer HCO+ (greater than or equal to 94%) and the minor produc t is CH3O+ The reaction of CH3+ with NH3 has two binary channels with the dominant product ion CH2NH2+ (> 70%) and the minor product ion NH4 + (approximate to 10%) and three body association channel with product CH3NH3+ (approximate to 20% at 0.32 Torr). The rate coefficient of th is reaction is decreasing nearly by one order of magnitude with increa sing E-r from near thermal up to 0.8 eV, for E-r > 0.8 eV the rate coe fficient increases with increasing Er. The experimental results are in terpreted in terms of a simple model assuming the reactions to proceed via the formation of long-lived collision complexes.