Synchrotron radiation and long path cryogenic cells: New tools and results for modelling chlorinated compounds absorption in the 8-12µm atmospheric window

 

Anusanth Anantharajah^a, Fridolin Kwabia Tchana^a, Jean-Marie Flaud^a , Pascale Roy^b and Laurent Manceron^b,c

• a- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), UMR CNRS 7583,
  Université de Paris et Université Paris-Est Créteil, Institut Pierre Simon Laplace,
  61 Avenue du Général de Gaulle, 94010 Créteil Cedex, France.
• b- Synchrotron SOLEIL, AILES Beamline, L’Orme des Merisiers, Saint-Aubin F-91192, France.
• c-  Sorbonne Université, CNRS, MONARIS, UMR 8233, 4 place Jussieu, F-75005 Paris, France. 

 

Nitryl chloride (ClNO₂) and Chlorine Nitrate are molecules of great interest for atmospheric chemistry since these are produced by heterogeneous reactions, in the marine troposphere, between NaCl sea-salt aerosols or ClO and gaseous N₂O₅ [1,2], and on polar stratospheric clouds, between N₂O₅ and solid HCl [3,4].

 

Many high-resolution spectroscopic studies in the microwave and mid-infrared regions are available. However, these molecules present low-lying vibrational levels and thus numerous hot bands in the regions of the NOx stretching and bending mode absorptions in the 8-12 µm atmospheric transparency window which could serve for remote sensing and quantification of these species.

Fourier Transform Spectrometry is a useful technique to observe broad band high resolution spectra (0.001 cm^-1) of these molecules and a significant advantage is gained by combining interferometry with the high brightness of a synchrotron source [5]. At SOLEIL we have developed specific instrumentation to study such reactive molecules and a few results concerning chlorine-containing compounds will be presented.

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4. M. T. Leu, Geophys. Res. Lett. 15, 851-854 (1988).
5.  J-M. Flaud, A. Anantharajah, F. Kwabia Tchana, L. Manceron, J. Orphal, G. Wagner, and M. Birk, J Quant Spectrosc Radiat Transf 224, 217-221 (2019).