[en] Highlights: • New, accurate empirical potential energy surface for ozone. • High accuracy dipole moment surface. • Consistent intensities computed for the three atmospheric ozone infrared bands. Monitoring ozone concentrations in the Earth’s atmosphere using spectroscopic methods is a major activity which undertaken both from the ground and from space. However there are long-running issues of consistency between measurements made at infrared (IR) and ultraviolet (UV) wavelengths. In addition, key O₃ IR bands at 10 µm, 5 µm and 3 µm also yield results which differ by a few percent when used for retrievals. These problems stem from the underlying laboratory measurements of the line intensities. Here we use quantum chemical techniques, first principles electronic structure and variational nuclear-motion calculations, to address this problem. A new high-accuracy ab initio dipole moment surface (DMS) is computed. Several spectroscopically-determined potential energy surfaces (PESs) are constructed by fitting to empirical energy levels in the region below 7000 cm${}^{-1}$ starting from an ab initio PES. Nuclear motion calculations using these new surfaces allow the unambiguous determination of the intensities of 10 µm band transitions, and the computation of the intensities of 10 µm and 5 µm bands within their experimental error. A decrease in intensities within the 3 µm is predicted which appears consistent with atmospheric retrievals. The PES and DMS form a suitable starting point both for the computation of comprehensive ozone line lists and for future calculations of electronic transition intensities.

[en] Highlights: • New 1950 K absorption spectrum of water recorded in methane/air flame. • 2417 lines identified in the 6250–6670 cm${}^{-1}$ region. • 2030 of these lines are assigned using a new variational line list yielding 127 new water energy levels. An absorption spectrum of H₂¹⁶O at 1950 K is recorded in a premixed methane/air flat flame using a cavity-enhanced optical frequency comb-based Fourier transform spectrometer. 2417 absorption lines are identified in the 6250–6670 cm${}^{-1}$ region with an accuracy of about 0.01 cm${}^{-1}$. Absolute line intensities are retrieved using temperature and concentration values obtained by tunable diode laser absorption spectroscopy. Line assignments are made using a combination of empirically known energy levels and predictions from the new POKAZATEL variational line list. 2030 of the observed lines are assigned to 2937 transitions, once blends are taken into account. 126 new energy levels of H₂¹⁶O are identified. The assigned transitions belong to 136 bands and span rotational states up to $J=27$.

[en] Highlights: • Visible wavekength spectra of ammonia recorded at Kitt Peak in 1980 analysed. • Analysis uses combination differences and two variational linelists. • 234 and 107 lines assigned in the red and green regions respectively. Room temperature NH₃ absorption spectra recorded at the Kitt Peak National Solar Observatory in 1980 are analyzed. The spectra cover two regions in the visible: 15,200 – 15,700 cm${}^{-1}$ and 17,950 – 18,250 cm${}^{-1}$. These high overtone rotation-vibration spectra are analyzed using both combination differences and variational line lists. Two variational line lists were computed using the TROVE nuclear motion program: one is based on an ab initio potential energy surface (PES) while the other used a semi-empirical PES. Ab initio dipole moment surfaces are used in both cases. 95 energy levels with $J=1-7$ are determined from analysis of the experimental spectrum in the 5ν_NH (red) region and 46 for 6ν_NH (green) region. These levels span four vibrational bands in each of the two regions, associated with stretching overtones.