Reaction of Nitrogen Dioxide with Ice Surface at Low Temperature (≤170 K)

Abstract

We studied the adsorption and reaction of nitrogen dioxide gas on the surface of an ice film at temperatures of 100–170 K under ultrahigh vacuum (UHV) conditions. Cs+ reactive ion scattering (RIS) and low-energy sputtering (LES) techniques were used to identify and quantify the reactants and products on the surface of the ice film, in conjunction with the use of temperature-programmed desorption (TPD) to monitor the species desorbed. Temperature-ramping experiments were performed to examine the changes in the populations of these species as a function of temperature. Adsorption of NO2 gas on the ice film at <110 K produced physisorbed species that may possibly possess negative charge character (NO2δ-), as deduced from the NO2 and NO2– signals in the RIS and LES experiments. At 110–130 K, NO2δ- species were either desorbed as NO2 gas or converted to nitrous acid (HONO), NO3–, and H3O+ on the surface. Nitrous acid gas was desorbed at 140–160 K. The efficiency of conversion of NO2 to surface nitrous acid was...