Absolute absorption cross sections for selected lines of the OH stretch overtone 2ν1 of the cis-isomer of nitrous acid HONO have been measured in the range 6623.6-6645.6 cm-1 using the continuous wave cavity ring-down spectroscopy (cw-CRDS) technique. HONO has been generated by two different, complementary methods: in the first method, HONO has been produced by pulsed photolysis of H2O2/NO mixture at 248 nm, and in the second method HONO has been produced in a continuous manner by flowing humidified N2 over 5.2 M HCl and 0.5 M NaNO2 solutions. Laser photolysis synchronized with the cw-CRDS technique has been used to measure the absorption spectrum of HONO produced in the first method, and a simple cw-CRDS technique has been used in the second method. The first method, very time-consuming, allows for an absolute calibration of the absorption spectrum by comparison with the well-known HO2 absorption cross section, while the second method is much faster and leads to a better signal-to-noise ratio. The strongest line in this wavelength range has been found at 6642.51 cm-1 with σ = (5.8 ± 2.2) × 10-21 cm2.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry