Kinetics and photochemistry of NO3. Part 1.—Absolute absorption cross-section

Abstract

The free radical NO₃ was generated by the reaction of NO₂ with ozone. A recirculating flow system was used so that concentrations of ozone ≈ 5 × 10¹⁷ molecule cm^–3 could be used. The absorption spectrum of NO₃ in the wavelength range 498–671 nm was obtained.

An absolute absorption cross-section was obtained at λ≈ 662 nm by using reactant concentrations such that all NO₂ was converted to NO₃ and no NO₃ was lost: that is, the [NO₂] added provided the absolute measure of [NO₃] in the system. The conditions used were [NO₂] [graphic omitted] 10¹² molecule cm^–3; [O₃] [graphic omitted] 3 × 10¹⁷ molecule cm^–3. At the absorption peak (λ≈ 663 nm) the cross-section is (121 ± 20)× 10^–19 cm² at T= 294 ± 4 K. A comparison is given of this value with the results of other workers, and some implications for the photochemistry of NO₃ are suggested.