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The Water Molecule: Line Position and Line Intensity Analyses up to the Second Triad

The Water Molecule: Line Position and Line Intensity Analyses up to the Second Triad. L. H. Coudert, a G. Wagner, b M. Birk, b and J.-M. Flaud a. a Laboratoire Interuniversitaire des Systèmes Atmosphériques, France b Deutsches Zentrum für Luft- und Raumfahrt e.V., Institut für

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The Water Molecule: Line Position and Line Intensity Analyses up to the Second Triad

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  1. The Water Molecule: Line Position and Line Intensity Analyses up to the Second Triad L. H. Coudert,a G. Wagner,b M. Birk,b and J.-M. Flauda aLaboratoire Interuniversitaire des Systèmes Atmosphériques, France bDeutsches Zentrum für Luft- und Raumfahrt e.V., Institut für Methodik der Fernerkundung, Germany

  2. Water facts Water is one of the most studied molecules In the Journal of Molecular Spectroscopy, 16 articles were published since June 2005 including: 15 experimental papers and 1 theoretical paper A theoretician has a lot of work to do just fitting these data

  3. The vibrational states involved Eight first vibrational states Data base for the n2 band region

  4. Overview • The theoretical approach • The line position analysis • The data set • Results • The line strength analysis • The spectroscopic parameters • The new measurements • Results • Building a new data base for water

  5. The theoretical approach The bending-rotation approach will be used. It accounts for the anomalous centrifugal distortion and for the Coriolis- and Fermi-type couplings. It has already been used in many investigations1-7and for the MIPAS8and HITRAN 20049data bases. Radau Coordinates 1. J. Mol. Spec.154, 427 (1992). 2. J. Mol. Spec.165, 406 (1994). 3.J. Mol. Spec.181, 246 (1997). 4.J. Mol. Spec. 195, 54 (1999). 5.Mol. Phys.96, 941 (1999). 6.J. Mol. Spec.206, 83 (2001). 7.J. Mol. Spec.228, 471 (2004). 8. J. Atmos. Oceanic Opt.16, 172 (2003). 9.J. Q. S. R. T.96, 139 (2005).

  6. Line position analysis: the data set Larger data set than in a previous investigation.1 15583 data including: • 2990 experimental energy levels • 12252 FIR and IR transitions • 341 microwave transitions Unitless Standard deviation is 1.4 1The eight first vibrational states of the water molecule: measurements and analysis, Coudert, Pirali, Vervloet, Lanquetin, and Camy-Peyret, J. Mol. Spec.228, 471 (2004).

  7. Results for transitions involving the(000) & (010) states

  8. Results for transitions involvingthe 1st triad states

  9. [1] Results for transitions involvingthe 2nd triad states The present approach does not take into account interaction with (2v20), (1v21), (0v22) states 1. R. A. Toth, J.Q.S.R.T.94, 51 (2005)

  10. Results for the microwave data 1. Matsushima, Odashima, Iwasaki, Tsunekawa, Takagi, J. Mol. Struct. 352/353, 371 (1995). 2. Matsushima, Tomatsu, Nagai, Moriwaki, Takagi, J. Mol. Spectrosc. 235, 194 (2006).

  11. Portion of the O-C Table for (010) A Watson-type Hamiltonian cannot be used for water. The calculated line positions should be accurate enough to build a data base for water. 1. Matsushima et al. (2006). 2. This work

  12. Line intensity analysis: the model

  13. The new measurements • Toth, J.Q.S.R.T.94, 51 (2005) 3n2, n1+n2, n3+n2, 3n2-n2, n1+n2-n2, n3+n2-n2 1559 transitions • This work n2, 2n2-n2 879 transitions

  14. Experimental • Instrument: Bruker IFS 120 HR • Sample cells: Short cell, White cell • Wavenumber range 1250-1750 cm-1 • MOPD: 187.5 cm • Optical path evacuated • Detector: Photoconductive MCT • Temperature measurement: Calibrated Pt100 + Lakeshore temperature controller • Pressure measurement: Thermostated, calibrated MKS Baratrons: 1, 10, 100, 1000, 5000 mb More details see presentation by Georg Wagner: „Water Pressure Broadening: A Never-ending Story“

  15. Measurement conditions + Analysis Pure water + air-broadened measurements Advantage: no instrumental lineshape errors in air-broadened data, different opacities for same transition Linestrength by averaging (2-20 measurements/averaged line),  of averaging ca. 1.3 on average Ca. 600 2 lines with overall uncertainty <2% Air-broadened number densities scaled.Reason: Number density more accurate in pure water measurementScaling factors differ <1% from 1!!

  16. Quality assessment, 2, main isotopomer Fit of scalar factor and temperature of individual pure water measurement. Reference: new linestrength data Ideal: T=296K, factor=1 Agreement good!! Independentanalysis of optical depths 0-0.5 and 0.5-4 Agreement good!!

  17. Strong linestrength-dependent difference to Toth data (currently in Hitran 2004) Origin to be investigated

  18. The available data All these data have not been fitted together

  19. The two line strength analyses Analysis I: The previous data except the measurements carried out in this work. Analysis II:The previous data except Toth’s measurements for transitions involving the n2 and 2n2-n2bands.

  20. Results for Analysis I 6159 data fitted. Std = 1.4

  21. M = J+1 R(J) M=JQ(J) M = -JP(J) AA

  22. Results for Analysis II 5558 data fitted. Std = 1.3

  23. Calculated with Hitran04

  24. Can we improve Hitran 04 ? • Using the results of Analysis II, a data base was built. • This new data base was compared with Hitran 04.

  25. Comparison for n2 band transitions Frequency diagram for S(new)-S(H04) in % of S(new) All Transitions

  26. Comparison for n2 band transitions Frequency diagram for S(new)-S(H04) in % of S(new) DKa= 1 Transitions

  27. Comparison for n2 band transitions Frequency diagram for S(new)-S(H04) in % of S(new) DKa> 1 Transitions

  28. Future work

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