title: The primary photodynamics of aqueous nitrate: formation of peroxynitrite.
abstract: We have examined the photochemical reactions occurring after irradiation at 200 nm of the aqueous nitrate ion, NO3(-)(aq). Using femtosecond transient absorption spectroscopy over the range 194-388 nm, we have characterized the formation and subsequent relaxation of the primary photoproducts of nitrate photolysis. The dominant photoproduct is the cis-isomer of peroxynitrite, which accounts for 48% of the excited state molecules initially produced. A slightly smaller fraction, 44%, of the excited molecules return to the electronic ground state of NO3(-) and relax to the vibrational ground state in 2 ps. The remaining 8% of the molecules initially excited react via the *NO + *O2(-) or the NO- + O2 dissociation channels. Formation of NO2(-) and *NO2 is not observed, suggesting that the previous observations of these species in steady-state photolysis are caused by reactions occurring on a longer time scale.
authors.affiliation: Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000, Aarhus, Denmark.
authors.forename: Dorte
authors.initials: D
authors.lastname: Madsen
authors.forename: Jane
authors.initials: J
authors.lastname: Larsen
authors.forename: Svend Knak
authors.initials: SK
authors.lastname: Jensen
authors.forename: Søren R
authors.initials: SR
authors.lastname: Keiding
authors.forename: Jan
authors.initials: J
authors.lastname: Thøgersen