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HOx and NOx production in oxidation flow reactors via photolysis of isopropyl nitrite, isopropyl nitrite-d7, and 1,3-propyl dinitrite at λ = 254, 350, and 369 nm

Abstract. Oxidation flow reactors (OFRs) are an emerging technique for studying the
formation and oxidative aging of organic aerosols and other applications. In
these flow reactors, hydroxyl radicals (OH), hydroperoxyl radicals
(HO2), and nitric oxide (NO) are typically produced in the following
ways: photolysis of ozone (O3) at λ=254 nm, photolysis of
H2O at λ=185 nm, and via reactions of O(1D) with
H2O and nitrous oxide (N2O); O(1D) is formed via
photolysis of O3 at λ=254 nm and/or N2O at
λ=185 nm. Here, we adapt a complementary method that uses alkyl
nitrite photolysis as a source of OH via its production of HO2 and NO
followed by the reaction NO + HO2 → NO2 + OH. We
present experimental and model characterization of the OH exposure and
NOx levels generated via photolysis of C3 alkyl nitrites
(isopropyl nitrite, perdeuterated isopropyl nitrite, 1,3-propyl dinitrite) in
the Potential Aerosol Mass (PAM) OFR as a function of photolysis wavelength
(λ=254 to 369 nm) and organic nitrite concentration (0.5 to 20 ppm). We also apply this technique in conjunction with chemical ionization
mass spectrometer measurements of multifunctional oxidation products
generated following the exposure of α-Pinene to HOx and
NOx obtained using both isopropyl nitrite and O3 + H2O + N2O as the radical precursors.
