Abstract. 

We present a novel photolytic source of gas-phase NO₃ suitable for use in atmospheric chemistry studies that has several advantages over traditional sources that utilize NO₂ + O₃ reactions and/or thermal dissociation of dinitrogen pentoxide (N₂O₅). The method generates NO₃ via irradiation of aerated aqueous solutions of ceric ammonium nitrate (CAN, (NH₄)₂Ce(NO₃)₆) and nitric acid (HNO₃) or sodium nitrate (NaNO₃). We present experimental and model characterization of the NO₃ formation potential of irradiated CAN / HNO₃ and CAN / NaNO₃ mixtures containing [CAN] = 10⁻³ to 1.0 M, [HNO₃] = 1.0 to 6.0 M, [NaNO₃] = 1.0 to 4.8 M, photon fluxes (I) ranging from 6.9 × 10¹⁴ to 1.0 × 10¹⁶ photons cm⁻² s⁻¹, and irradiation wavelengths ranging from 254 to 421 nm. NO₃ mixing ratios ranging from parts per billion to parts per million by volume were achieved using this method. At the CAN solubility limit, maximum [NO₃] was achieved using [HNO₃] ≈ 3.0 to 6.0 M and UVA radiation (λ_max = 369 nm) in CAN / HNO₃ mixtures or [NaNO₃] ≥ 1.0 M and UVC radiation (λ_max = 254 nm) in CAN / NaNO₃ mixtures. Other reactive nitrogen (NO₂, N₂O₄, N₂O₅, N₂O₆, HNO₂, HNO₃, HNO₄) and reactive oxygen (HO₂, H₂O₂) species obtained from the irradiation of ceric nitrate mixtures were measured using a NO_x analyzer and an iodide-adduct high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS). To assess the applicability of the method for studies of NO₃-initiated oxidative aging processes, we generated and measured the chemical composition of oxygenated volatile organic compounds (OVOCs) and secondary organic aerosol (SOA) from the β-pinene + NO₃ reaction using a Filter Inlet for Gases and AEROsols (FIGAERO) coupled to the HR-ToF-CIMS.