Molecular line shape studies for atmospheric remote sensing
by NGUYEN Thi Huyen Trang
by NGUYEN Thi Huyen Trang
This thesis is devoted to accurate predictions of the shapes of absorption transitions for three important greenhouse gases: CO2, N2O, and H2O, under atmospheric pressure and temperature conditions. In the first part of the thesis, some general definitions of molecular spectroscopy and a brief introduction of various line-shape models used in the thesis will be presented. Linear molecular systems (i.e. CO2, N2O) will be investigated in the second part. In the latter, requantized classical molecular dynamics simulations (rCMDS) were performed for CO2 diluted in O2 (and N2) at various temperatures using a site-site intermolecular potential. The simulations were made for a large range of the Doppler widths, covering near-Doppler to collision-dominant regimes. The Fourier-Laplace transform of the auto-correlation functions of the dipole moment, calculated by rCMDS, leads to the associated spectra of CO2 broadened by O2 (N2). All the effects of collisions between CO2 and O2 (N2) molecules (e.g. the speed-dependent, Dicke narrowing and line-mixing effects) are included in the simulated spectra. Line-shape parameters were then deduced by fitting the simulated spectra with the quadratic speed-dependent Nelkin–Ghatak profile but also other models including the Voigt, the quadratic speed-dependent Voigt and the Hartmann-Tran profiles. The collisional broadening coefficient, its speed dependence, the Dicke narrowing and the first-order line-mixing parameters were retrieved using a multi-spectrum fitting procedure. The temperature dependences of these parameters were then obtained through the use of a single power law. The parameters obtained for CO2/O2 were then combined with those for CO2/N2 in order to deduce parameters for CO2 in air. A similar study was then performed for N2O diluted in air. The third part will be devoted to water vapor, an asymmetric-top molecule. In this case, we use the partially-correlated speed-dependence Keilson-Storer model whose parameters are deduced from molecular dynamic simulations and semi-classical calculations. This model takes into account the collision-induced velocity-changes effects, the speed dependences of the collisional line width and shift as well as the correlation between velocity and internal-state changes. For each considered transition, the model is corrected by a parameter deduced from its broadening coefficient measured for a single pressure. The corrected- partially-correlated speed-dependence Keilson-Storer model is then used to simulate the shapes of H2O rovibrational lines broadened by N2, over a wide pressure range. All the predicted results in part two and three will be compared with measured data showing very good agreements.
References.
[1] N.H. Ngo, H.T. Nguyen, H. Tran, Precise predictions of H2O line shapes over a wide pressure range using simulations corrected by a single measurement, J Quant Spectrosc Transf, 2018, 207, 16–22.
[2] Nguyen HT, Ngo NH, Tran H, Prediction of line shapes parameters and their temperature dependences for CO2-N2 using molecular dynamics simulations, J Chem Phys, 2018, 149, 224301.
[3] H. T. Nguyen, N. H. Ngo, and H. Tran, Line-shape parameters and their temperature dependences predicted from molecular dynamics simulations for O2- and air-broadened CO2 lines, J. Chem. Phys, 2020, 242, 106729.
[4] N.H. Ngo, H.T. Nguyen, M.T.Le, H. Tran, Air-broadened N2O line-shape parameters and their temperature dependences by requantized classical molecular dynamics simulations, J Quant Spectrosc Transf, 2021, 267, 107067.
[5] Nguyen Thi Huyen Trang, Le Cong Tuong, Ngo Ngoc Hoa, Model Kelson-Storer and the spectroscopic parameters in the near-infrared of pure water vapor, Advances in Optics Photonics Spectroscopy and Applications X, 2019, 125.
[6] Ngo Ngoc Hoa, P.Chelin, X. Landsheere, M. Schwell, Nguyen Thi Huyen Trang, Le Cong Tuong, New measurements of Carbon Dioxide absorption in the 1.6micrometer region, Advances in Optics Photonics Spectroscopy and Applications X, 2019, 25.
[2] Nguyen HT, Ngo NH, Tran H, Prediction of line shapes parameters and their temperature dependences for CO2-N2 using molecular dynamics simulations, J Chem Phys, 2018, 149, 224301.
[3] H. T. Nguyen, N. H. Ngo, and H. Tran, Line-shape parameters and their temperature dependences predicted from molecular dynamics simulations for O2- and air-broadened CO2 lines, J. Chem. Phys, 2020, 242, 106729.
[4] N.H. Ngo, H.T. Nguyen, M.T.Le, H. Tran, Air-broadened N2O line-shape parameters and their temperature dependences by requantized classical molecular dynamics simulations, J Quant Spectrosc Transf, 2021, 267, 107067.
[5] Nguyen Thi Huyen Trang, Le Cong Tuong, Ngo Ngoc Hoa, Model Kelson-Storer and the spectroscopic parameters in the near-infrared of pure water vapor, Advances in Optics Photonics Spectroscopy and Applications X, 2019, 125.
[6] Ngo Ngoc Hoa, P.Chelin, X. Landsheere, M. Schwell, Nguyen Thi Huyen Trang, Le Cong Tuong, New measurements of Carbon Dioxide absorption in the 1.6micrometer region, Advances in Optics Photonics Spectroscopy and Applications X, 2019, 25.