Cross-sections and quantum yields for the atmospheric photolysis of the potent greenhouse gas nitrogen trifluoride

Although NF₃, a trace gas of purely anthropogenic origin with a large global warming potential is accumulating in the Earth's atmosphere, little photochemical data exists from which to calculate its atmospheric removal rate. In this study, photodissociation quantum yields, Φ₁, were derived following 193.3 nm laser photolysis of NF₃, and quantitative conversion of the F-atom photoproducts to OH, which was detected by laser induced fluorescence. Values of Φ₁(P, T) = (1.03 ± 0.05) were determined at pressures between 28 and 100 mBar of He or N₂ and at either room temperature or 255 K. Absorption cross-sections, σ, obtained between 184 and 226 nm were combined with the values of Φ₁(P, T) to confirm a long (≈700 year) photolysis lifetime for NF₃. No evidence for reaction of OH with NF₃ was found, indicating that this process makes little or no contribution to NF₃ removal from the atmosphere. These results underpin recent calculations of an NF₃ atmospheric lifetime τ ≈ 550 years, largely controlled by photolysis in the stratosphere. In the course of this work the rate coefficient k₂(298 K) = (1.3 ± 0.2) × 10^?11 cm³ molecule^?1 s^?1 was obtained for the reaction F + H₂O.