Relative Rates and Their Dependence on Kinetic Energy for Ion–Molecule Reactions in Ammonia

Ion cyclotron resonance techniques are used to measure the relative rates and their dependence on kinetic energy for the major ion–molecule reactions in ammonia. Charge transfer is shown to compete with proton transfer in the reaction of both NH2+ and NH3+ with ammonia over an energy range from thermal velocities to 50 eV: NH4++NH2k1↗NH3++NH3k4↘NH3++NH3, NH4++NHk2↗NH2++NH3k3↘NH3++NH2. The rate for charge transfer increases with increasing kinetic energy while the rate for proton transfer decreases with kinetic energy. At thermal kinetic energies, k2 / k1 = 0.6 and k3 / k2 = 1.0. Resonant charge transfer from NH3+ was observed only for translationally excited ions.