1. 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

2. CNRS-LISAMSS 2006, Columbus, June 19-23, 20062 H 2 O: 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 Motivation Motivation 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

3. CNRS-LISAMSS 2006, Columbus, June 19-23, 20063 Motivation Motivation Solar Spectrum with Atmospheric Absorptions

4. CNRS-LISAMSS 2006, Columbus, June 19-23, 20064 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). Previous measurement in the near IR region Example of measurement: line intensities ( S  10 23 /cm molecule -1 ) position (cm -1 )HITRAN04PonsardinSchermaulRay 12014.14311.679---1.9601.504 12218.82481.8652.1852.2901.888 12244.72333.2363.815.080--- 12244.78730.88861.08--- ! Differences between different authors exceed stated accuracy (up to 30%)  need for more measurements

5. CNRS-LISAMSS 2006, Columbus, June 19-23, 20065 Chopper Wavemeter ECDLDFG ECDL (External External Cavity Diode Laser) and DFG (Difference Frequency Generation Laser) coupled with multi-path absorption cell: Experimental set-up Mid IR 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

6. CNRS-LISAMSS 2006, Columbus, June 19-23, 20066 Experimental set-up 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

7. CNRS-LISAMSS 2006, Columbus, June 19-23, 20067 Experimental set-up L = 1 m, maximum path length 100 m, CaF 2 windows 3 MKS Baratrons Water sample Thermometer

8. CNRS-LISAMSS 2006, Columbus, June 19-23, 20068 Experimental Precautions HDO lines (probed in the mid-IR by the DFG laser) to validate H 2 O 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) H 2 O samples: Distilled, ultrasonic …

9. CNRS-LISAMSS 2006, Columbus, June 19-23, 20069  10 10  ResultsResults Example1: Self broadening of the line at 12226.101 cm -1 Very high S/N ratio( >1000) Experimental lines very well modeled using Voigt profile Observation of « Dicke narrowing »

10. CNRS-LISAMSS 2006, Columbus, June 19-23, 200610 10   10 ResultsResults Example2: Air-broadening of the line at 12226.101 cm -1

11. CNRS-LISAMSS 2006, Columbus, June 19-23, 200611 ResultsResults Example3: 3 lines near 12259 cm-1

12. CNRS-LISAMSS 2006, Columbus, June 19-23, 200612 Results : Line Intensities 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 Fixed Free

13. CNRS-LISAMSS 2006, Columbus, June 19-23, 200613 Results : Self-broadening coefficient 40 lines measured RMS < 1% 10 % lower than HITRAN2004

14. CNRS-LISAMSS 2006, Columbus, June 19-23, 200614 Results : Air-broadening coefficient 40 lines measured RMS < 1% Very good agreement with HITRAN2004 (less than 5%)

15. CNRS-LISAMSS 2006, Columbus, June 19-23, 200615 Conclusion and prospective 40 different H 2 O 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 ?