Quantification of the absorption cross sections of surface-adsorbed nitric acid in the 335–365 nm region by Brewster angle cavity ring-down spectroscopy

We have quantified absorption cross sections of surface-adsorbed HNO3 in the 335–365 nm region at 295 K by using Brewster angle cavity ring-down spectroscopy. Absorption cross sections for HNO3 adsorbed on fused silica surfaces ranged between (3.1 ± 0.5) × 10−19 and (0.44 ± 0.04) × 10−19 cm2/molecule in the wavelength region studied. The HNO3 surface cross section values are at least two orders of magnitude larger than HNO3 cross section values of about <3 × 10−22 cm2/molecule in the gas phase over the 335–350 nm range. Our results support the field-observed large differences between nitric acid photolysis rates on the surface and that of the gas phase.