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Laser spectroscopic study of ozone in the 100←000 band for the SWIFT instrument

Laser spectroscopic study of ozone in the 100←000 band for the SWIFT instrument. M. Guinet, C. Janssen, D. Mondelain, C. Camy-Peyret LPMAA, CNRS- UPMC (France). 18/06/2010. In the stratosphere: UV filter for solar radiation Key role in tropospheric chemistry (OH radical precursor)

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Laser spectroscopic study of ozone in the 100←000 band for the SWIFT instrument

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  1. Laser spectroscopic study of ozone in the 100←000 band for the SWIFT instrument M. Guinet, C. Janssen, D. Mondelain, C. Camy-Peyret LPMAA, CNRS- UPMC (France) 18/06/2010

  2. In the stratosphere:UV filterfor solar radiation Key role intropospheric chemistry(OH radical precursor) Green house gas Studied by alarge palette of instruments(UV spectrophotometer, Dobson spectrometer, FTIR…) 1% uncertaintyfor intensity is required for atmospheric applications (reactive gas!) Comparison of published data sets →several % inconsistenciesfor intensities (10 µm bands) Importance of ozone in terrestrial atmosphere

  3. Stratospheric Wind Interferometer For Transport studies (SWIFT) • O3: tracer for atmospheric winds (SWIFT instrument) • Stratospheric wind speed (Doppler shift) & ozone concentration measurements • Understand thetransport of O3in the stratosphere High accuracies required(for the 15 strong 16O3 transitions) - Absolute positions:  5  10-5 cm-1 (  13 m s-1) - Absoluteintensities:  1% Other spectroscopic parameters measured: air, air, self

  4. A set up at the border of metrology and spectroscopy Stabilization principle Stabilized HeNe / = 10-8 633 nm Laser Diode / < 4.10-8 8.9 µm Michelson interferometer

  5. A set up at the border of metrology and spectroscopy Stabilization principle Stabilized HeNe / = 10-8 Stabilized HeNe / = 10-8 633 nm Laser Diode / < 4.10-8 Laser Diode / < 4.10-8 8.9 µm Michelson interferometer

  6. A set up at the border of metrology and spectroscopy Stabilization principle Stabilized HeNe / = 10-8 Stabilized HeNe / = 10-8 633 nm Laser Diode / < 4.10-8 Laser Diode / < 4.10-8 8.9 µm Michelson interferometer

  7. A set up at the border of metrology and spectroscopy Stabilization principle Stabilized HeNe / = 10-8 Stabilized HeNe / = 10-8 633 nm Laser Diode / < 4.10-8 Laser Diode / < 4.10-8 8.9 µm Michelson interferometer

  8. A set up at the border of metrology and spectroscopy Stabilization principle Stabilized HeNe / = 10-8 Stabilized HeNe / = 10-8 633 nm Laser Diode / < 4.10-8 Laser Diode / < 4.10-8 8.9 µm Michelson interferometer Both highly tunable and stabilized system Ultra flexible setup (atmospheric windows accessible) Amplitude modulation scheme good S/N (several thousand)

  9. Stabilized spectrometer N2O D Laser Diode D (FP) PT 100 C D UV O3 Interferometer locked onto stabilized HeNelaser O3 Generation D UV O3 Generation system Step by step mode Step < 10-4 cm-1 S/N : 3000 I0 N2O Accuracy (2): Position < 8.10-5 cm-1 Intensity < 2% FP LaserDiode M. Guinet,D. Mondelain, C. Janssen, C. Camy-Peyret, JQSRT,111, 961-972 (2010)

  10. Spectra 10 000 points SWIFT Line Linearization Absolute calibration

  11. Metrological approach  Reduction and taking into account of systematic biases: Sample purity, spectrometer, experimental conditions… Traceability : Following the BIPM recommendation (photometer UV). Calibrated tools (PT 100, micrometer, pressure gauge, stabilized HeNe). Expertise : O3 sample purity test (> 99.5 % purity sample) : IR spectrometer (CO2, H2O, N2O) mass spectrometer (N2, NOx) pressure (O2, N2, non condensable gases), Stable conditions (temperature, very low ozone decomposition 2- 4 ‰ / hour) Checking : Check BIPM UV recommended cross section (Hearn) with a calibrated pressure gauge.  Mass spectrometer   Hearn A. G., Proc. Phys. Soc., 78 (1961) 932-940 C. Janssen and M. Guinet, RSI., submitted

  12. High accuracy absorption measurement of O3 cross section at 253.65 nm International standard (BIPM) :  = 1.14710-17cm² (± 2.1%) our measures :  = 1.13110-17cm² (± 0.7%) M. Guinet, C. Camy-Peyret, D. Mondelain and C. Janssen, Refinement of the ozone standard – absolute ozone absorption cross section at the mercury emission line position 253.65 nm, Metrol., en préparation

  13. Estimated uncertainties between 0.8 and 1.3% considering: statistical error over the 11 spectra with pure O3 systematic errors (T, offset, UV, LUV, LIR…) Results on intensities Comparison with HITRAN08: -2.2  1.1(2) % (Our UV cross section) -2.6  1.3(2) (Mauersberger cross section)

  14. Cross cell : UV and IR measured simultaneously 3.6% inconsistencies between UV (Hearn) and IR (HITRAN 08) recommended values in agreement with Picquet-Varrault Results on intensities IR UV Picquet-Varrault et al, J. Phys. Chem A, 109 (2005) 1008-1014.

  15. The N2O line positions were accurately measured by an heterodyne experiment (Maki and Wells) Linearization and calibration procedure applied to O3 and N2O spectra Absolute positions of strong O3 lines N2O positions → overall accuracy of 8 10-5 cm-1 (2)  Wind speed uncertainty: ~ 20 m s-1 O3 positions → Mean difference with HITRAN08: (5  8 (2))10-5 cm-1 Maki A.G., Wells J.S. NIST Special publication (1991) 821

  16. Determination of the self pressure broadening Pressure broadening at 2 % accuracy level (2) Agrees with HITRAN by 0.6% with Smith by 1.7% (Voigt profile) • Ultra high resolution spectra • (200 – 1000 points / line) • Voigt and Rautian-Sobel'man • (hard) line profile • Multi-fit procedure

  17. Air-pressure broadening coefficients 8 absorption spectrarecorded with the crossed UV-IR cell and a 50 m astigmatic cell (O3 decomposition <1% / hour) Astigmatic cell

  18. Air Pressure Shift Temperature dependence: Determination of air and air at 240 K → nair and nair Temperature regulated cell Voigt profile Smith M. A. H., Malati Devi V., Benner D. C., Rinsland C. P., J. Mol. Spectrosc. 182 (1997) 239-259.

  19. Conclusion 253 nm UV cross section determination Our IR measurement are 2.2 % higher than HITRAN 08 3.6% inconsistencies between UV (Hearn) and IR (HITRAN 08) recommended values Position in agreement with HITRAN 08 Measurement of temperature dependence of air broadening and air shifting.

  20. Laser spectroscopic study of ozone in the 100←000 band for the SWIFT instrument M. Guinet, C. Janssen, D. Mondelain, C. Camy-Peyret LPMAA, CNRS- UPMC (France) 18/06/2010

  21. Jitter of the Laser diode 3.7 10-5 cm-1 The line is used like a frequency/amplitude noise converter

  22. Limb view dl Intensity Wave number Stratospheric Wind Interferometer For Transport studies (SWIFT) Stratospheric wind velocity Doppler effect O3 à 1133,4 cm-l 5.10-5 cm-1 13 m.s-1

  23. Repeatability of the determination of the laser line shape We fit the instrument’s apparatus function like a Voigt profile Set of 32 (on two day) measure in a sealed N2O cell The intensity, lorentz (210-4 cm-1) , gaussian (410-4 cm-1) are fit on the spectrum Intensity ± 9‰ ‰ ± 4% lorentz Exemple of TDL Line Shape : J. Reid, D. T. Cassidy, and R. T. MenziesLinewidth measurements of tunable diode lasers using heterodyne and etalon techniques November 1982 / Vol. 21, No. 21 / APPLIED OPTICS

  24. UV O3 Generation system I0 N2O FP LaserDiode Stabilized spectrometer Accuracy (1): Position < 4.10-5 cm-1 Intensity < 1%

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