The temperature dependence (203–293 K) of the absorption cross sections of O 3 in the 230–850 nm region measured by Fourier-transform spectroscopy

Abstract

Absolute absorption cross sections of O 3 were measured in the 230–850 nm (11765–43478 cm −1) region at five different temperatures (203–293 K) using a Fourier-transform spectrometer, at a spectral resolution of 5.0 cm −1 (corresponding to about 0.027 nm at 230 nm and to about 0.36 nm at 850 nm). The spectral accuracy of the data is better than 0.1 cm −1 — about 0.5 pm at 230 nm and about 7.2 pm at 850 nm — validated by recording of I 2 absorption spectra in the visible using the same experimental set-up. O 3 absorption spectra at different concentrations were recorded at five different sample temperatures in the range 203–293 K, and at each temperature at two total pressures (100 and 1000 mbar) using O 2/N 2 mixtures as buffer gas. Within the limits of experimental uncertainties, no influence of total pressure on the O 3 spectrum was observed in the entire spectral region, as expected from the short lifetimes of the upper electronic states of O 3. The temperature dependence of the O 3 absorption cross sections is particularly strong in the Huggins bands between 310 and 380 nm, as observed in previous studies. An empirical formula is used to model the temperature dependence of the O 3 absorption cross sections between 236 and 362 nm, a spectral region that is particularly important for atmospheric remote-sensing and for photochemical modelling.