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

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.