Molecular dynamic simulations of N2-broadened methane line shapes and comparison with experiments

Tuong Le Cong, J. L. Doménech, M. Lepère, Ha Tran

Résultats de recherche: Recherche - Revue par des pairsArticle

Résumé

Absorption spectra of methane transitions broadened by nitrogen have been calculated for the first time using classical molecular dynamic simulations. For that, the time evolution of the auto-correlation function of the dipole moment vector, assumed along a C-H axis, was computed using an accurate site-site intermolecular potential for CH4-N2. Quaternion coordinates were used to treat the rotation of the molecules. A requantization procedure was applied to the classical rotation and spectra were then derived as the Fourier-Laplace transform of the auto-correlation function. These computed spectra were compared with experimental ones recorded with a tunable diode laser and a difference-frequency laser spectrometer. Specifically, nine isolated methane lines broadened by nitrogen, belonging to various vibrational bands and having rotational quantum numbers J from 0 to 9, were measured at room temperature and at several pressures from 20 to 945 mbar. Comparisons between measured and calculated spectra were made through their fits using the Voigt profile. The results show that ab initio calculated spectra reproduce with very high fidelity non-Voigt effects on the measurements and that classical molecular dynamic simulations can be used to predict spectral shapes of isolated lines of methane perturbed by nitrogen.

langueAnglais
Numéro d'article094305
journalThe journal of chemical physics
Volume146
Numéro9
Les DOIs
étatPublié - 7 mars 2017

Empreinte digitale

Methane
Molecular dynamics
Nitrogen
Computer simulation
Experiments
line shape
methane
molecular dynamics
simulation
nitrogen
Autocorrelation
autocorrelation
Dipole moment
Laplace transforms
Electron transitions
Semiconductor lasers
Spectrometers
Absorption spectra
Fourier transforms
Molecules

Citer ceci

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title = "Molecular dynamic simulations of N2-broadened methane line shapes and comparison with experiments",
abstract = "Absorption spectra of methane transitions broadened by nitrogen have been calculated for the first time using classical molecular dynamic simulations. For that, the time evolution of the auto-correlation function of the dipole moment vector, assumed along a C-H axis, was computed using an accurate site-site intermolecular potential for CH4-N2. Quaternion coordinates were used to treat the rotation of the molecules. A requantization procedure was applied to the classical rotation and spectra were then derived as the Fourier-Laplace transform of the auto-correlation function. These computed spectra were compared with experimental ones recorded with a tunable diode laser and a difference-frequency laser spectrometer. Specifically, nine isolated methane lines broadened by nitrogen, belonging to various vibrational bands and having rotational quantum numbers J from 0 to 9, were measured at room temperature and at several pressures from 20 to 945 mbar. Comparisons between measured and calculated spectra were made through their fits using the Voigt profile. The results show that ab initio calculated spectra reproduce with very high fidelity non-Voigt effects on the measurements and that classical molecular dynamic simulations can be used to predict spectral shapes of isolated lines of methane perturbed by nitrogen.",
author = "{Le Cong}, Tuong and Doménech, {J. L.} and M. Lepère and Ha Tran",
year = "2017",
month = "3",
doi = "10.1063/1.4976978",
volume = "146",
journal = "The journal of chemical physics",
issn = "0021-9606",
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Molecular dynamic simulations of N2-broadened methane line shapes and comparison with experiments. / Le Cong, Tuong; Doménech, J. L.; Lepère, M.; Tran, Ha.

Dans: The journal of chemical physics, Vol 146, Numéro 9, 094305, 07.03.2017.

Résultats de recherche: Recherche - Revue par des pairsArticle

TY - JOUR

T1 - Molecular dynamic simulations of N2-broadened methane line shapes and comparison with experiments

AU - Le Cong,Tuong

AU - Doménech,J. L.

AU - Lepère,M.

AU - Tran,Ha

PY - 2017/3/7

Y1 - 2017/3/7

N2 - Absorption spectra of methane transitions broadened by nitrogen have been calculated for the first time using classical molecular dynamic simulations. For that, the time evolution of the auto-correlation function of the dipole moment vector, assumed along a C-H axis, was computed using an accurate site-site intermolecular potential for CH4-N2. Quaternion coordinates were used to treat the rotation of the molecules. A requantization procedure was applied to the classical rotation and spectra were then derived as the Fourier-Laplace transform of the auto-correlation function. These computed spectra were compared with experimental ones recorded with a tunable diode laser and a difference-frequency laser spectrometer. Specifically, nine isolated methane lines broadened by nitrogen, belonging to various vibrational bands and having rotational quantum numbers J from 0 to 9, were measured at room temperature and at several pressures from 20 to 945 mbar. Comparisons between measured and calculated spectra were made through their fits using the Voigt profile. The results show that ab initio calculated spectra reproduce with very high fidelity non-Voigt effects on the measurements and that classical molecular dynamic simulations can be used to predict spectral shapes of isolated lines of methane perturbed by nitrogen.

AB - Absorption spectra of methane transitions broadened by nitrogen have been calculated for the first time using classical molecular dynamic simulations. For that, the time evolution of the auto-correlation function of the dipole moment vector, assumed along a C-H axis, was computed using an accurate site-site intermolecular potential for CH4-N2. Quaternion coordinates were used to treat the rotation of the molecules. A requantization procedure was applied to the classical rotation and spectra were then derived as the Fourier-Laplace transform of the auto-correlation function. These computed spectra were compared with experimental ones recorded with a tunable diode laser and a difference-frequency laser spectrometer. Specifically, nine isolated methane lines broadened by nitrogen, belonging to various vibrational bands and having rotational quantum numbers J from 0 to 9, were measured at room temperature and at several pressures from 20 to 945 mbar. Comparisons between measured and calculated spectra were made through their fits using the Voigt profile. The results show that ab initio calculated spectra reproduce with very high fidelity non-Voigt effects on the measurements and that classical molecular dynamic simulations can be used to predict spectral shapes of isolated lines of methane perturbed by nitrogen.

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