The surface photochemistry of nitric acid (HNO3) adsorbed on hematite (a-Fe2O3) particle surfaces under different environmental conditions has been studied. Surface product formation and photochemistry of adsorbed nitrate is investigated using X-ray photoelectron spectroscopy (XPS). Adsorbed nitrate, formed from gas phase nitric acid adsorption, shows N1s peak at 407.4 eV. Upon irradiation with light (? > 300 nm), the coverage of nitrate decreases, as indicated by the decrease in the peak at 407.4 eV, and there is the appearance of two lower binding energy peaks in the N1s region at 401.7 eV and 400.3 eV when the photolysis is done under low to moderate relative humidity conditions. The formation as well as the stability of these reduced nitrogen species, identified as NO- and N-, is further investigated as a function of water vapor pressure. Additionally, irradiation of adsorbed nitrate on a-Fe2O3 generates three nitrogen containing gas-phase products including NO2, NO and N2O as evident by FTIR spectroscopy. As shown here, different environmental conditions of water vapor pressure and the presence of molecular oxygen greatly influence the relative product distribution of gas-phase and surface-bound species. The atmospheric implications of these results are discussed.

Photochemistry of adsorbed nitrate formed from nitric acid adsorption on a-Fe<sub>2</sub>O<sub>3</sub> particle surfaces: The role of adsorbed water in the formation of reduced nitrogen surface species

247th National Meeting (2014)

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Photochemistry of adsorbed nitrate formed from nitric acid adsorption on a-Fe2O3 particle surfaces: The role of adsorbed water in the formation of reduced nitrogen surface species

Photochemistry of adsorbed nitrate formed from nitric acid adsorption on a-Fe₂O₃ particle surfaces: The role of adsorbed water in the formation of reduced nitrogen surface species