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Quantitative Spectroscopy Using IR Lasers

DIODE- AND DIFFERENCE-FREQUENCY LASER STUDIES OF ATMOSPHERIC MOLECULES IN THE NEAR- AND MID-INFRARED: H 2 O, NH 3 , and NO 2. Johannes ORPHAL , Pascale CHELIN, Nofal IBRAHIM, and Pierre-Marie FLAUD

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Quantitative Spectroscopy Using IR Lasers

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  1. DIODE- AND DIFFERENCE-FREQUENCY LASER STUDIES OF ATMOSPHERIC MOLECULES IN THE NEAR- AND MID-INFRARED: H2O, NH3, and NO2 Johannes ORPHAL, Pascale CHELIN, Nofal IBRAHIM, and Pierre-Marie FLAUD Laboratoire Interuniversitaire des Systèmes Atmosphériques Université de Paris-12, Créteil, France

  2. Quantitative Spectroscopy Using IR Lasers • Tunable diode-lasers are available in the near-infrared region: 0.7 – 2.0 mm (optical telecommunication) • Extremely useful for quantitative spectroscopy of atmospheric molecules (many studies in the last 5 years) • Very high-resolution (less than 0.0001 cm-1) with external cavities • Many photons (at least a few mW) on output • High signal/noise ratio (a few 1000) in short measurement time • Single wavelength, tunable over several 10 nms (a few 100 cm-1) • A laser based on difference-frequency generation can “transport” these properties into the mid-infrared (3 – 5 mm) • This talk: applications to H2O, NH3, NO2 9th International HITRAN Conference, Cambridge, June 26, 2006

  3. External Cavity Diode-Lasers • Toptica DL-100 (“Littrow” configuration) • grating forms part of the cavity • linewidth 1 MHz (0.00003 cm-1) • output power up to 30 mW • spectral range: 810 – 880 nm (11360 – 12350 cm-1) 1535 – 1565 nm (6390 – 6515 cm-1) • tunable range (single mode) at least 20-30 GHz (0.6-1.0 cm-1) • relatively small beam divergence 9th International HITRAN Conference, Cambridge, June 26, 2006

  4. External Cavity Diode-Lasers • H2O absorption line around 830 nm 9th International HITRAN Conference, Cambridge, June 26, 2006

  5. 3 MKSBaratrons Water sample Thermometer L = 1 m, maximum path length 100 m, CaF2 windows White-type absorption cell 9th International HITRAN Conference, Cambridge, June 26, 2006

  6. The H2O band around 822 nm 9th International HITRAN Conference, Cambridge, June 26, 2006

  7. Previous measurements of H2O around 822 nm • 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) ! Differences between different authors exceed stated accuracy (up to 30%)  need for more measurements 9th International HITRAN Conference, Cambridge, June 26, 2006

  8. Experimental Precautions • H2O samples: distilled, cleaned by ultrasonic procedure • Calibrating the MKS Baratron heads • Validation of detector linearity using neutral density filters • Linearization of the wavenumber axis: FP etalon (1 MHz) • Simultaneous recording of HDO lines (in the mid-IR using a DFG laser) to validate H2O pressure values (assumption: natural HDO abundance); result: less than 2 % deviations • Background emission of the ECDL  narrow spectral filter • Validate analysis software with synthetic lines 9th International HITRAN Conference, Cambridge, June 26, 2006

  9. 10 10 Results from LISA Example 1: Self-broadening of the line at 12226.101 cm-1 • High S/N ratio( >1000) • Experimental lines well reproduced using Voigt profile • Weak residuals due to Dicke narrowing 9th International HITRAN Conference, Cambridge, June 26, 2006

  10. 10 10 Results from LISA Example 2: Air-broadening of the line at 12226.101 cm-1 • Again: weak residuals due to Dicke narrowing (even at 200 Torr) 9th International HITRAN Conference, Cambridge, June 26, 2006

  11. Results from LISA Example 3: Self-broadening of 3 lines near 12259 cm-1 • Note: the Dicke-narrowing also affects the baseline between the lines 9th International HITRAN Conference, Cambridge, June 26, 2006

  12. FixedFree Line intensities • Note: • Straight lines (1-2 %) • Up to 10 % difference between fixed and free D in the Voigt profile • MEAN value (!) 15 % above HITRAN2004 • Good agreement (5 %)with Ponsardin and Browell, JMS 1997 • Difference can not be explained by line profile 9th International HITRAN Conference, Cambridge, June 26, 2006

  13. Self-broadening • Note: • Straight line (1 %) • BUT: 10 % lower than HITRAN2004 9th International HITRAN Conference, Cambridge, June 26, 2006

  14. Air-broadening • Note: • Straight line (< 1 %) • Good agreement with HITRAN2004 (< 5 %) 9th International HITRAN Conference, Cambridge, June 26, 2006

  15. Conclusions for H2O around 822 nm • 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 line intensities using other profiles (Galatry, Rautian,…) • Perform new, independent experiments (FTS?) • Strategies for H2O broadening in HITRAN 9th International HITRAN Conference, Cambridge, June 26, 2006

  16. External Cavity Diode-Lasers • Toptica DL-100 (“Littrow” configuration) • grating as part of the cavity • linewidth 1 MHz (0.00003 cm-1) • output power up to 30 mW • spectral range: 810 – 880 nm (11360 – 12350 cm-1) 1535 – 1565 nm (6390 – 6515 cm-1) • tunable range (single mode) at least 20-30 GHz (0.6-1.0 cm-1) • relatively low beam divergence 9th International HITRAN Conference, Cambridge, June 26, 2006

  17. External Cavity Diode-Lasers • Toptica DL-100 (“Littrow” configuration) • output power up to 30 mW • Photo-acoustic spectroscopy (PAS) 9th International HITRAN Conference, Cambridge, June 26, 2006

  18. Thanks to Prof. Th. Huet, University of Lille, France Photoacoustic Spectroscopy of NH3 around 1.5 mm • Reminder: How works PAS • Photoacoustic effect:Collisional energy transfer • Laser tuned to a molecular transition:  Excited molecules  Partly, non radiative de-excitation  Temperature changes  Pressure changes  Acoustic wave  Detection by microphone 9th International HITRAN Conference, Cambridge, June 26, 2006

  19. Photoacoustic Spectroscopy of NH3 around 1.5 mm • Simultaneous direct absorption measurements using a White-type multiple-pass cell 9th International HITRAN Conference, Cambridge, June 26, 2006

  20. Photoacoustic Spectroscopy of NH3 around 1.5 mm • Simultaneous direct absorption measurements using a White-type multiple-pass cell 9th International HITRAN Conference, Cambridge, June 26, 2006

  21. Photoacoustic Spectroscopy of NH3 around 1.5 mm Spectral calibration using the FTS line positions of Lundsberg-Nielsen et al. (1993) 9th International HITRAN Conference, Cambridge, June 26, 2006

  22. Photoacoustic Spectroscopy of NH3 around 1.5 mm 1 2 3 Problem: The relative line intensities seem to be incorrect:Lines No. 2 and 3 should be very similar, about 60 % of the line No. 1 Check with direct absorption spectra 9th International HITRAN Conference, Cambridge, June 26, 2006

  23. Absorption Spectroscopy of NH3 around 1.5 mm 1 2 3 Spectral calibration using the FTS line positions of Lundsberg-Nielsen et al. (1993) 9th International HITRAN Conference, Cambridge, June 26, 2006

  24. Absorption Spectroscopy of NH3 around 1.5 mm 9th International HITRAN Conference, Cambridge, June 26, 2006

  25. Absorption Spectroscopy of NH3 around 1.5 mm Problem: The relative line intensities seem to be incorrect:Lines No. 2 and 3 should be very similar, about 60 % of the line No. 1 The fitted Doppler widths are not equal ! Spectral calibration using the FTS line positions of Lundsberg-Nielsen et al. (1993) 9th International HITRAN Conference, Cambridge, June 26, 2006

  26. Absorption Spectroscopy of NH3 around 1.5 mm New absorption spectra using FTS: • Bruker IFS 120 HR Fourier spectrometer (Orsay) • Absorption cell 25 cm, CaF2 windows • NH3 pressure 30 mbar • Spectral range 5950 – 7850 cm-1 • Spectral resolution 0.02 cm-1 9th International HITRAN Conference, Cambridge, June 26, 2006

  27. Absorption Spectroscopy of NH3 around 1.5 mm 14NH3 15NH3 9th International HITRAN Conference, Cambridge, June 26, 2006

  28. Absorption Spectroscopy of NH3 around 1.5 mm Comparison of the NH3 line positions (example) 14NH3 15NH3 • (*) calibrated using the IUPAC recommended standard: H2O lines of Toth, accuracy (RMS) 0.0005 cm-1 The new NH3 linelist is available in digital format upon request to the authors. 9th International HITRAN Conference, Cambridge, June 26, 2006

  29. Chopper Wavemeter Mid-IR NO2 line intensities using a DFG laser • DFG (Difference Frequency Generation) Laser) • ECDL: • 30 mW • 810 - 880 nm • Linewidth 1 MHz • DFG • 3 - 5 µm • Linewidth 1MHz • Lock-in detection • LabView acquisition • S/N>1000 • Measurement time: few minutes Mid IR 9th International HITRAN Conference, Cambridge, June 26, 2006

  30. Mid-IR NO2 line intensities using a DFG laser • DFG (Difference Frequency Generation) Laser) • ECDL: • 30 mW • 810 - 880 nm • Linewidth 1 MHz • DFG • 3 - 5 µm • Linewidth 1MHz • Lock-in detection • LabView acquisition • S/N>1000 • Measurement time: few minutes 9th International HITRAN Conference, Cambridge, June 26, 2006

  31. Mid-IR NO2 line intensities using a DFG laser • DFG (Difference Frequency Generation) Laser) • ECDL: • 30 mW • 810 - 880 nm • Linewidth 1 MHz • DFG • 3 - 5 µm • Linewidth 1MHz • Lock-in detection • LabView acquisition • S/N>1000 • Measurement time: few minutes 9th International HITRAN Conference, Cambridge, June 26, 2006

  32. II.1. Caractérisation instrumentale: spectroscopie de N2O. Validation of the DFG using N2O, CH4 and HI Mid-IR NO2 line intensities using a DFG laser Interféromètre de Fabry Pérot, Validation avec N2O. PN2O = 0.075 mbar 9th International HITRAN Conference, Cambridge, June 26, 2006

  33. II.1. Caractérisation instrumentale: spectroscopie de N2O. Validation of the DFG using N2O, CH4 and HI Mid-IR NO2 line intensities using a DFG laser Interféromètre de Fabry Pérot, Validation avec N2O. PN2O = 7,5.10-2 mbar RMS deviation 0.00006 cm-1 9th International HITRAN Conference, Cambridge, June 26, 2006

  34. II.1. Caractérisation instrumentale: spectroscopie de N2O. Validation of the DFG using N2O, CH4 and HI Mid-IR NO2 line intensities using a DFG laser Interféromètre de Fabry Pérot, Validation avec N2O. RMS deviation 0.7 % 9th International HITRAN Conference, Cambridge, June 26, 2006

  35. Spectre d’absorption de la bande fondamentale de HI. Validation of the DFG using N2O, CH4 and HI Mid-IR NO2 line intensities using a DFG laser Bande d’absorption υ1 R(0) 9th International HITRAN Conference, Cambridge, June 26, 2006

  36. Spectre d’absorption de la bande fondamentale de HI. Validation of the DFG using N2O, CH4 and HI Mid-IR NO2 line intensities using a DFG laser Bande d’absorption υ1 9th International HITRAN Conference, Cambridge, June 26, 2006

  37. II.2. Intensités de raies de NO2. NO2 concentrations determined using the VIS Mid-IR NO2 line intensities using a DFG laser Motivations 9th International HITRAN Conference, Cambridge, June 26, 2006

  38. II.2. Intensités de raies de NO2. NO2 concentrations determined using the VIS Mid-IR NO2 line intensities using a DFG laser Motivations 9th International HITRAN Conference, Cambridge, June 26, 2006

  39. II.2. Intensités de raies de NO2. NO2 concentrations determined using the VIS Mid-IR NO2 line intensities using a DFG laser Motivations 9th International HITRAN Conference, Cambridge, June 26, 2006

  40. II.2. Intensités de raies de NO2. Typical mid-IR spectrum and fit (residuals × 25) (υ1+ υ2+ υ3)- υ2 υ1+ υ3 résidu x 25 PNO2 = 2 mbar Mid-IR NO2 line intensities using a DFG laser Motivations 9th International HITRAN Conference, Cambridge, June 26, 2006

  41. II.2. Intensités de raies de NO2. Mid-IR NO2 line intensities using a DFG laser Motivations 9th International HITRAN Conference, Cambridge, June 26, 2006

  42. II.2. Intensités de raies de NO2. Results for the “cold” band n1+n3 27 lines measured Mean deviation wrt. HITRAN2004: - 4.9 % ± 1.2 % Results for the “hot” band (n1+n2+n3) - n2 8 lines measured (many lines are blended) Mean deviation wrt. HITRAN2004: - 2.3 % ± 1.2 % Line positions of the “hot” band (n1+n2+n3) - n2 slightly shifted (see also Perrin et al., 1997) Mid-IR NO2 line intensities using a DFG laser Motivations 9th International HITRAN Conference, Cambridge, June 26, 2006

  43. Conclusions • Using ECDL for studying line intensities and shapes in the near- and mid-IR, at very high S/N and spectral resolution • DFG lasers can “transport” these properties into the mid-infrared (3 – 5 mm) and possibly at longer wavelengths • H2O: line intensities of the 822 nm band 15 % too low • NH3: new NIR line list recorded using FTS • NO2: very good agreement between UV and IR at 3 mm • Further studies: H2CO, O3, HO2 … 9th International HITRAN Conference, Cambridge, June 26, 2006

  44. Acknowledgements • Pierre-Marie Flaud (PhD, 2003-2005) • Nofal Ibrahim (PhD, 2003-2006) • CNRS Department “Sciences Physique et Mathématiques” • University of Paris-12 Créteil 9th International HITRAN Conference, Cambridge, June 26, 2006

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