Nofal IBRAHIM, Pascale CHELIN, Johannes ORPHAL LINE PARAMETERS OF WATER VAPOR IN THE NEAR- AND MID-INFRARED REGIONS DETERMINED USING TUNEABLE LASER SPECTROSCOPY Nofal IBRAHIM, Pascale CHELIN, Johannes ORPHAL Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) Université de Paris-XII, 91405 Créteil Cedex, France YURI I. BARANOV Optical Technology Division, NIST, Gaithersburg, MD 20899-8441, USA

Motivation H2O: The most important atmospheric trace gas It has a crucial role in the Earth's radiation budget (responsible for ~70% of absorption of incoming sunlight ) Principal contributor to the greenhouse effect Absorption of solar radiation in the near-IR region Infrared remote sensing of atmosphere using aircraft and satellite sensors Necessity to provide: precise spectral line parameters in the near-IR region CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Solar Spectrum with Atmospheric Absorptions Motivation Solar Spectrum with Atmospheric Absorptions CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Previous measurement in the near IR region R. A. Toth, J. Mol. Spectrosc., 166, 176-183 (1994). J.-M. Flaud et al., J. Mol. Spectrosc., 185, 211-221 (1997). P. L. Ponsardin et al., J. Mol. Spectrosc., 185, 58-70 (1997). A. Lucchesini et al., Eur. Phys. J. D., 8, 223-226 (2000). R. Schermaul et al, J. Mol. Spectrosc. 208, 32-42 (2001). A. Ray et al., Appl. Phys. B, 79, 915-921(2004). Example of measurement: line intensities (S1023/cm molecule-1) position (cm-1) HITRAN04 Ponsardin Schermaul Ray 12014.1431 1.679 --- 1.960 1.504 12218.8248 1.865 2.185 2.290 1.888 12244.7233 3.236 3.81 5.080 12244.7873 0.8886 1.08 ! Differences between different authors exceed stated accuracy (up to 30%)  need for more measurements CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Experimental set-up ECDL (External External Cavity Diode Laser) and DFG (Difference Frequency Generation Laser) coupled with multi-path absorption cell: Chopper Wavemeter ECDL: 30 mW 810-880 nm Linewidth 1MHz DFG 3-5 µm Linewidth 1MHz Lock-in detection LabVIEW acquisition S/N>1000 Measurement time: few minutes Mid IR CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Experimental set-up ECDL: DFG Lock-in detection LabVIEW acquisition 30 mW 810-880 nm Linewidth 1MHz DFG 3-5 µm Linewidth 1MHz Lock-in detection LabVIEW acquisition S/N>1000 Measurement time: few minutes CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

L = 1 m, maximum path length 100 m, CaF2 windows Experimental set-up L = 1 m, maximum path length 100 m, CaF2 windows 3 MKS Baratrons Water sample Thermometer CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Experimental Precautions HDO lines (probed in the mid-IR by the DFG laser) to validate H2O pressure values (assumption: natural HDO abundance). Background emission of the ECDL  narrow spectral filter. Validation of detector linearity using neutral density filters. Linearization of the wavenumber axis: FP etalon (1MHz) H2O samples: Distilled, ultrasonic … CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Example1: Self broadening of the line at 12226.101 cm-1 Results Example1: Self broadening of the line at 12226.101 cm-1 10 10 Very high S/N ratio( >1000) Experimental lines very well modeled using Voigt profile Observation of « Dicke narrowing » CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Example2: Air-broadening of the line at 12226.101 cm-1 Results Example2: Air-broadening of the line at 12226.101 cm-1 10  10 CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Example3: 3 lines near 12259 cm-1 Results Example3: 3 lines near 12259 cm-1 CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Results : Line Intensities Fixed Free Up to 10 % between fixed and free D Voigt profile MEAN value (!) 15 % above HITRAN2004 Good agreement (5%) with Ponsardin and Browell, JMS 1997 Difference can not be explained by line profile CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Results : Self-broadening coefficient 40 lines measured RMS < 1% 10 % lower than HITRAN2004 CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Results : Air-broadening coefficient 40 lines measured RMS < 1% Very good agreement with HITRAN2004 (less than 5%) CNRS-LISA MSS 2006, Columbus, June 19-23, 2006

Conclusion and prospective 40 different H2O lines measured between 815 and 835 nm. Intensities in the 830 nm band 15% higher than HITRAN2004. Self-broadening coefficients 10% lower than HITRAN2004. Air-broadening coefficients in good agreement (< 5%) with HITRAN2004. Dicke-narrowing  although weak, check impact on intensities using other profiles (Galatry, Rautian,…) New, independent experiments (FTS?) Update of HITRAN2004 ? CNRS-LISA MSS 2006, Columbus, June 19-23, 2006