title: Spectroscopic study of HNO3 dissociation on ice.
abstract: A detailed spectroscopic study of HNO(3):H(2)O binary amorphous mixtures, and of the adsorption of HNO(3) onto ice, is reported. Using a classical optics model, the extent of intermixing and of ionic dissociation of adsorbed HNO(3), which forms a strong acid with liquid water, is determined as a function of HNO(3) coverage and temperature. Even at temperatures as low as 45 K, where intermixing is limited to at most a few molecular layers at the interface, ionic dissociation of adsorbed HNO(3) is observed to be extensive. While some amount of molecularly adsorbed HNO(3) is observed at the surface of ice at 45 K, its ionic dissociation occurs irreversibly upon heating the ice substrate to 120 K. The molecularly adsorbed state of HNO(3) is not restored upon cooling, suggesting HNO(3) is a metastable entity at the surface of ice. Therefore, despite ionic dissociation of HNO(3) being thermodynamically favored, it appears to be kinetically inhibited at the surface of amorphous solid water at temperatures below 120 K.
authors.affiliation: Département de Chimie, Université de Sherbrooke, 2500, boulevard université, Sherbrooke, Québec J1K 2R1, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Marchand
authors.forename: Guillaume
authors.initials: G
authors.lastname: Marcotte
authors.forename: Patrick
authors.initials: P
authors.lastname: Ayotte
mesh_terms: D000327:Adsorption; D007053:Ice; D017942:Nitric Acid / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D007053:Ice; D017942:Nitric Acid