1. Line Strength Measurements in the n2 band of H218O
Yu. I. Baranov,a P. Chelin,b J. Orphal,b
and L. H. Coudertb
aInstitute of Experimental Meteorology, Obninsk, Russia
bLISA, CNRS/Paris 12 University, Créteil, France

2. Overview Line position analysis: data and results The new spectra
Analysis of the n2 band line strengths
Natural abundance of H218O is 0.2%.
Used to monitor water vapor transport in the atmosphere.1
1. Keith, J. Geophysical Research Atmospheres 105, (2000).

3. Line position analysis
3 sets of data:
Experimental energy levels
Wavenumbers of FIR and IR transitions
Frequencies of Terahertz and microwave lines
The anomalous centrifugal distortion is accounted for using
the Bending-rotation approach.1
1. Coudert et al., J. Molec . Spectrosc. 251, 339 (2008).

4. Line position analysis results: levels
Maximum J-value is 15
We go up to Ka = 15 only for the ground state.

5. Line position analysis results: transitions
5591 data points. s = 1.7

6. Experimental conditions

7. One of the new spectra P = 4.28 Torr, L = 24 cm, T = 23.5°C
H218O with 97% purity from CAMPRO

8. Line intensity determination
Lines were fitted
to a Voigt profile

9. Comparison with Toth’s values
We are about 10% below Toth’s values.

10. Analysis of the n2 band line strengths
791 transitions fitted. s = 1.0
18 parameters varied.

11. Portion of the O-C table for Ka > 4
For the 719 transitions belonging to the n2 band.
(O - C)% = 6.1 (Toth) and (This work)

12. Building a data base
Using the results of both analyses, a data base was built and the spectrum of the n2 band was computed.

13. Observed
Calculated

14. Observed
Adding 0.3 Torr
of H216O
Calculated

15. Line position analysis results: microwave transitions
5591 data points. s = 1.7