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 Methodik der Fernerkundung, Germany

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

Eight first vibrational states The vibrational states involved Data base for the 2 band region

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

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. 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). Radau Coordinates It has already been used in many investigations 1-7 and for the MIPAS 8 and HITRAN data bases.

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

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

Results for transitions involving the 1 st triad states

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

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).

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

Line intensity analysis: the model

Toth, J.Q.S.R.T. 94, 51 (2005) 3 2, 1  2, 3  2, 3 2  2, 1    2, 3  2  transitions This work 2, 2 2  transitions The new measurements

Experimental Instrument: Bruker IFS 120 HR Sample cells: Short cell, White cell Wavenumber range cm -1 MOPD: 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“

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 lines with overall uncertainty <2% Air-broadened number densities scaled. Reason: Number density more accurate in pure water measurement Scaling factors differ <1% from 1!!

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!! Independent analysis of optical depths and Agreement good!!

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

The available data All these data have not been fitted together

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 2 and    2 bands.

Results for Analysis I 6159 data fitted. Std = 1.4

M  J  R  J  M  J Q(J) M  J P(J) AA

Results for Analysis II 5558 data fitted. Std = 1.3

Calculated with Hitran04

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.

Comparison for 2 band transitions Frequency diagram for S(new)  S(H04) in % of S(new) All Transitions

Comparison for 2 band transitions Frequency diagram for S(new)  S(H04) in % of S(new)  Ka  1 Transitions

Comparison for 2 band transitions Frequency diagram for S(new)  S(H04) in % of S(new)  Ka  1 Transitions

Future work