Pressure and temperature dependences of the ‘‘binary’’ ion–molecule reaction N+3+H2O→H2NO++N2

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Abstract
Experiments were carried out using a time‐resolved atmospheric pressure ionization mass‐spectrometer (TRAPI) in N2–H2O (∼1 ppm) system at temperatures from 233 to 543 K and at pressures from 167 to 760 Torr. The title reaction showed temperature and pressure dependences which were explained by the following scheme: N+3+H2O⇄(N+3⋅H2O)* (forward and backward rate constants ka and kb; (N+3⋅H2O)*→H2NO++N2 (forward rate constant kp; (N+3⋅H2O)* +N2→H2NO++2N2 (forward rate constant ka. Assuming that kd is equal to the collision rate constant of 7.1×10−10 cm3 s−1, the individual rate constants were determined as ka =2.8×10−9 cm3 s−1 (302 K), kb =17T3.6 s−1 where T is temperature in K, and kp =2.0×109 s−1 (302 K). The product H2NO+ ion changed by successive reactions with H2O into H2NO+⋅H2O and subsequently to H3O+.