High Resolution Infrared Spectroscopy in Support of Ozone Atmospheric Monitoring and Validation of the Potential Energy Function

The first part of this review is a brief reminder of general information concerning atmospheric ozone, particularly related to its formation, destruction, observations of its decrease in the stratosphere, and its increase in the troposphere as a result of anthropogenic actions and solutions. A few words are said about the abandonment of the Airbus project Alliance, which was expected to be the substitute of the supersonic Concorde. This project is over due to the theoretical evaluation of the impact of a fleet in the stratosphere and has been replaced by the A380, which is now operating. The largest part is devoted to calculations and observations of the transitions in the infrared range and their applications for the atmosphere based both on effective models (Hamiltonian, symmetry rules, and dipole moments) and ab initio calculations. The complementarities of the two approaches are clearly demonstrated, particularly for the creation of an exhaustive line list consisting of more than 300,000 lines reaching experimental accuracies (from 0.00004 to 0.001 cm-1) for positions and a sub percent for the intensities in the 10 microns region. This contributes to definitively resolving the issue of the observed discrepancies between line intensity data in different spectral regions: between the infrared and ultraviolet ranges, on the one hand, and between 10 and 5 microns on the other hand. The following section is devoted to the application of recent work to improve the knowledge about the behavior of potential function at high energies. A controversial issue related to the shape of the potential function in the transition state range near the dissociation is discussed.

Ab Initio Insight into Mechanisms of Ozone Interaction with a Surface of Dehydrated Nanocrystalline TiO2

Density functional theory (DFT) study of ozone adsorption on dehydrated nanocrystalline TiO₂ is presented. Singlet and triplet binding modes of ozone to the oxide's titanium cations are considered. In both the modes, monodentate and bidentate ozone complexes are formed. According to DFT, the triplet monodentates are the most stable species. The formation of monodentate ozone adsorption complexes is in-line with an earlier interpretation of infrared (IR) spectroscopic data on ozone adsorption on an anatase surface. However, the computed difference in the fundamental vibrational frequencies (ν₁ - ν₃) of ozone in the triplet monodentates is significantly larger than the corresponding IR value. This discrepancy is resolved by demonstrating that the triplet monodentates readily decompose, realizing molecular oxygen that is consistent with published experimental data. The predicted energy barrier of the dissociative adsorption is less than 2 kcal/mol. In contrast, the computed difference in the fundamental vibrational frequencies (ν₁ - ν₃) of adsorbed ozone in the singlet bidentates perfectly agrees with the experiment.

Spectroscopic studies of ozone in cryosolutions: FT-IR spectra of 16O3 in liquid nitrogen, oxygen, argon and krypton

We have measured and interpreted the IR spectra of ozone dissolved in liquid nitrogen, oxygen, argon, and krypton in the 650-4700cm^-1 spectral region at 79-117K. Frequency shifts, band intensities and bandshapes of 22 spectral features of soluted ozone were analyzed. The bands of the А₁ symmetry have a complex contour and possess an excess intensity with respect to the value of the purely vibrational transition moment. It was found that this effect is related to the manifestation of the Coriolis interaction. The bandshape distortion manifests itself as an additional intensity from the side of the В₁ symmetry band being an intensity source in the case of the Coriolis interaction.

Intercomparison of Simultaneously Obtained Infrared (4.8 μm) and Visible (515−715 nm) Ozone Spectra Using ACE-FTS and MAESTRO

Laboratory ozone absorption spectra were measured simultaneously in the visible (515-715 nm) and infrared (2070-2140 cm(-1)) spectral regions using SCISAT-1's MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and ACE-FTS (Atmospheric Chemistry Experiment-Fourier Transform Spectrometer) spectrometers. An intercomparison of these measurements was used to assess the relative accuracy of HITRAN absolute line strengths, for which there was a 4% change between the 2000 and 2004 versions. Results reported here show that Chappuis band cross section strengths are more consistent with the HITRAN 2004 4.8 microm band line strengths than with the 2000 compilation.

Concentration measurements of ozone in the 1200-300ppbv range: an intercomparison between the BNM ultraviolet standard and infrared methods

Simultaneous ultraviolet (UV) and infrared (IR) measurements of ozone concentration in air in the 1200-300 ppbv range have been performed using the ultraviolet absorption in the Hartley band at 0.2537 microm and the infrared absorption of a doublet at 9.507 microm in the nu(3) vibration-rotation band. Infrared concentration measurements were achieved using the tunable diode laser spectrometer of LPMA in Paris with interferometric control of the emitted wavelength while the UV concentration measurements were performed with the 49PS Megatec ozone generator of the Bureau National de Metrologie (BNM). The simultaneous recording of spectra of a reference cell filled with pure distilled ozone and of a low concentration mixture inside a long absorbing path Herriott cell allows to carry out infrared concentration measurements with an accuracy of the same order as the ultraviolet ones and provides the instrumental parameters of the spectrometer corresponding to each concentration measurement, which reduces systematic errors. Within the respective absolute uncertainties proper to the two techniques, no systematic discrepancy was evidenced between the IR and the UV measurements. The ozone ultraviolet absorption coefficient value determined by Hearn (308.3 +/- 4 cm(-1)atm(-1)) and used by the BNM and the National Institute of Standards and Technology (NIST) is confirmed by the present work.