High-Resolution Spectroscopic Characterization of the ν2 saQ(6, 3) Rovibrational Transition of Ammonia, an Important Air-Quality Pollutant, Using an Ultra-Stable Laser Spectrometer
This paper reports a high-resolution spectroscopic study of the ν2 saQ(6, 3) rovibrational transition of ammonia (NH3) near 10 μm, performed with an ultra-stable laser. Forty-six absorption spectra were recorded at 300 K and 10 Pa and processed with an automated non-linear fitting procedure implemented in Python. Two line-shape models were compared: a Gaussian profile, accounting for Doppler broadening only, and a Voigt profile, obtained from the convolution of the Doppler and collisional (Lorentzian) contributions. The Gaussian model converged for all 46 spectra and provided a numerically robust estimate of the transition frequency, whereas the Voigt model, although physically more complete, converged for only 22 of the 46 spectra, reflecting its greater sensitivity to the signal-to-noise ratio and to baseline quality in the wings of the line. Residual analysis shows that a purely Doppler profile does not fully reproduce the observed line shape, while Voigt residuals remain structured for several spectra with lower spectral quality. The central frequency obtained in this work, 28,953,694.0613 MHz, is consistent with the range of previous experimental determinations of this transition and falls within about 1 MHz of the ab initio prediction, with the smallest deviation among the values compared, an observation that should be read as indicative rather than as a demonstration of superior accuracy, since no formal uncertainty budget is available for the present measurement. These results provide a methodological basis for further studies of pressure-broadening parameters and of the atmospheric applications of this transition.
References
[1]
Mejri, S., Sow, P.L.T., Tokunaga, S.K., Lopez, O., Goncharov, A., Argence, B., et al. (2014) Ultra-Stable Mid-IR Quantum Cascade Laser for High-Resolution Spectroscopy and Metrology. 2014 European Frequency and Time Forum (EFTF), Neuchatel, 23-26 June 2014, 239-240. https://doi.org/10.1109/eftf.2014.7331475
[2]
Kumar, P., Broquet, G., Hauglustaine, D., Beaudor, M., Clarisse, L., Van Damme, M., et al. (2025) Global Atmospheric Inversion of the Anthropogenic NH 3 Emissions over 2019-2022 Using the LMDZ-INCA Chemistry Transport Model and the IASI NH3 Observations. Atmospheric Chemistry and Physics, 25, 12379-12407. https://doi.org/10.5194/acp-25-12379-2025
[3]
Portejoie, S., Martinez, J. and Landmann, G. (2002) L’ammoniac d’origine agricole: Impacts sur la santé humaine et animale et sur le milieu naturel. INRAE Productions Animales, 15, 151-160. https://doi.org/10.20870/productions-animales.2002.15.3.3697
[4]
Krupa, S.V. (2003) Effects of Atmospheric Ammonia (NH3) on Terrestrial Vegetation: A Review. Environmental Pollution, 124, 179-221. https://doi.org/10.1016/s0269-7491(02)00434-7
[5]
Chen, S., Cheng, M., Guo, Z., Xu, W., Du, X. and Li, Y. (2020) Enhanced Atmospheric Ammonia (NH3) Pollution in China from 2008 to 2016: Evidence from a Combination of Observations and Emissions. Environmental Pollution, 263, Article 114421. https://doi.org/10.1016/j.envpol.2020.114421
[6]
Loubet, B. (2000) Modélisation du dép？t sec d’ammoniac atmosphérique à proximité des sources. Ph.D Thesis, Université Paul Sabatier.
[7]
Mohan, H. (1979) Molecules of Significance in Planetary Aeronomy. National Aeronautics and Space Administration, Scientific and Technical Information Office, 140.
[8]
Tran, D.B.A. (2019) Laser à cascade quantique infrarouge moyen stabilisé par peigne de fréquences, largement accordable et tra？able au SI: Application à des mesures spectroscopiques de haute précision de molécules polyatomiques. Ph.D. Thesis, Université Sorbonne Paris Nord.
[9]
Maaroufi, N. (2019) Détermination des paramètres spectroscopiques des bandes ν？ et ν3 de NH3 par spectroscopie infrarouge. Ph.D. Thesis, Université Paris Diderot.
[10]
Machin, L. (2006) étude théorique de l’excitation collisionnelle de l’ammoniac et de ses isotopomères deutérés dans le milieu interstellaire. Ph.D. Thesis, Université Pierre-et-Marie-Curie.
[11]
Sow, P.L.T. (2015) Développement d’un spectromètre laser à cascade quantique pour des applications en spectroscopie de haute résolution et en métrologie des fréquences. Ph.D. Thesis, Université Sorbonne Paris Nord.
[12]
Mejri, S., Sow, P.L.T., Kozlova, O., Ayari, C., Tokunaga, S.K., Chardonnet, C., et al. (2015) Measuring the Boltzmann Constant by Mid-Infrared Laser Spectroscopy of Ammonia. Metrologia, 52, S314-S323. https://doi.org/10.1088/0026-1394/52/5/s314
[13]
Urban, ？., Papou？ek, D., Kauppinen, J., Yamada, K. and Winnewisser, G. (1983) The ν2 Band of 1？NH3: A Calibration Standard with Better than 1 × 10？？ cm？1 Accuracy. Journal of Molecular Spectroscopy, 101, 1-15. https://doi.org/10.1016/0022-2852(83)90002-4
[14]
Marine, A. (2022) étude de profils spectraux de raies d’absorption infrarouge du protoxyde d’azote dilué dans de l’azote. Ph.D. Thesis, Université de Namur.
[15]
Larcher, G. (2016) Profil spectral des raies d’absorption du dioxyde de carbone en vue d’application à l’étude de l’atmosphère de la Terre par télédétection. Ph.D. Thesis, Université Pierre-et-Marie-Curie.
[16]
Marcadet, X., Carras, M., Maisons, G., De Naurois, G. and Simozrag, B. (2011) Les lasers à cascade quantique: L’accès au moyen infrarouge. Photoniques, 54, 54-57. https://doi.org/10.1051/photon/20115454
[17]
Cappelli, F., Galli, I., Borri, S., Giusfredi, G., Cancio, P., Mazzotti, D., et al. (2012) Subkilohertz Linewidth Room-Temperature Mid-Infrared Quantum Cascade Laser Using a Molecular Sub-Doppler Reference. Optics Letters, 37, Article 4811. https://doi.org/10.1364/ol.37.004811
[18]
Lemarchand, C., Triki, M., Darquié, B., Bordé, C.J., Chardonnet, C. and Daussy, C. (2011) Progress Towards an Accurate Determination of the Boltzmann Constant by Doppler Spectroscopy. New Journal of Physics, 13, Article 073028. https://doi.org/10.1088/1367-2630/13/7/073028
[19]
Magerl, G., Schupita, W., Frye, J.M., Kreiner, W.A. and Oka, T. (1984) Sub-Doppler Spectroscopy of the Ν2 Band of NH3 Using Microwave Modulation Sidebands of CO2 Laser Lines. Journal of Molecular Spectroscopy, 107, 72-83. https://doi.org/10.1016/0022-2852(84)90266-2
[20]
Lemarchand, C. (2012) Mesure de la constante de Boltzmann par spectroscopie laser: Vers une contribution au futur Système International d’unités. Ph.D. Thesis, Université Sorbonne-Paris-Nord.
[21]
Seigneur, C. and Cohen, E. (2002) Modélisation des particules dans l’atmosphère ambiante. Pollution Atmosphérique, Climat, Santé, Société, 174, 255-273.
[22]
Azouz, N. (2017) Modélisation des flux d’ammoniac aux échelles locale et régionale dans des paysages hétérogènes: Application à l’évaluation des dépassements des charges critiques. Ph.D. Thesis, Université Pierre et Marie Curie.
[23]
Consolino, L., Cappelli, F., de Cumis, M.S. and De Natale, P. (2019) QCL-Based Frequency Metrology from the Mid-Infrared to the Thz Range: A Review. Nanophotonics, 8, 181-204. https://doi.org/10.1515/nanoph-2018-0076
[24]
D’Amato, F., Barucci, M., Bianchini, G. and Viciani, S. (2025) Quantum Cascade Laser (QCL) in Airborne Atmospheric Measurements: A Review. Optics Express, 33, Article 22745. https://doi.org/10.1364/oe.558437
[25]
Saemian, M., Del Balzo, L., Gacemi, D., Todorov, Y., Rodriguez, E., Lopez, O., et al. (2024) Ultra-Sensitive Heterodyne Detection at Room Temperature in the Atmospheric Windows. Nanophotonics, 13, 1765-1772. https://doi.org/10.1515/nanoph-2023-0787
[26]
Laref, R. (2020) étude d’un système à base de micro-capteurs de gaz pour le suivi et la cartographie de la pollution atmosphérique. Ph.D. Thesis, Université de Lorraine.
[27]
Poupry, S. (2024) Contribution à la conception et à la mise en ？uvre d’un système de surveillance de la qualité de l’air: Application à la surveillance de la qualité de l’air dans les vallées des Gaves. Autre. Ph.D. Thesis, Institut National Polytechnique de Toulouse.
