Ion-molecule reactions of N3+, N4+, O2+, and NO2+ in nitrogen containing traces of oxygen

Abstract

A new sort of stationary pulsed afterglow method with a mass spectrometric analysis is presented to study quantitative ion behavior at atmospheric pressure. Repetitive x-ray pulses from an electron linear accelerator are used to ionize gases. Experiments were carred out in a system of nitrogen containing traces of oxygen. The ion–molecule reaction rate constants for N3++O2 and N4++O2 were measured as (7.1±0.7)×10−11 and (2.86±0.3)×10−10 cm3 s−1, respectively. A main cause for ±10% errors in the rate constants is attributed to errors of measurements of oxygen contents. An error due to ion sampling through the reactor wall aperture is evaluated to be less than ±0.5%. Thus, the presented method is very useful for accurate quantitative study. Product ion NO+2 is shown to be lost in nitrogen via successive reaction. The endothermic reaction NO+2+N2→NO++N2O with a rate constant of 1.2×10−15 cm3 s−1 is postulated. The rate constant of the exothermic reaction O+2+N2→NO++NO was found to be less than 2×10−18 cm3 s−1.