The NO and non-energetic OH radical reactivity: characterization and reaction scheme

Abstract

The solid phase reaction between NO and non-energetic OH radicals was investigated using helium as a dilution medium at 3 K. The species generated were characterized by in situ Fourier transform infrared (FTIR) spectroscopy. The choice of solid phase experiment was motivated by its potential applications in the field of atmospheric chemistry and astrochemistry. Unfortunately, under such conditions, broad absorption bands with overlapping features are observed, and as a consequence, the assignment of each signal to the newly formed specie is risky. This is the reason why, in order to attribute all the absorption bands observed in the solid phase FTIR spectra, similar experiments were carried out by replacing the dilution medium with neon whereas other experimental parameters were retained. As a result, all produced species are trapped in neon matrix showing narrow peaks so the elucidation of spectral signals is simple. Furthermore, the correlation of the spectra in solid phase and in neon matrix helps to avoid the intricacies in understanding the spectrum observed in solid phase reactivity. This approach allowed us to characterize the formation of nitrous acid (HONO), nitrogen dioxide (NO2), nitrosyl hydride (HNO), nitric acid (HNO3), nitrous oxide (N2O) and ozone (O3). The concentration effect of reagents on the end products was also investigated. Based on these experimental results, reaction pathways are proposed to explain the formation of all the observed products.