Transcript h218o.ppt

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
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, 15167 (2000).
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).
Line position analysis results: levels
Maximum J-value is 15
We go up to Ka = 15 only for the ground state.
Line position analysis results: transitions
5591 data points. s = 1.7
Experimental conditions
One of the new spectra
P = 4.28 Torr, L = 24 cm, T = 23.5°C
H218O with 97% purity from CAMPRO
Line intensity determination
Lines were fitted
to a Voigt profile
Comparison with Toth’s values
We are about 10% below Toth’s values.
Analysis of the n2 band line strengths
791 transitions fitted. s = 1.0
18 parameters varied.
Portion of the O-C table for Ka > 4
For the 719 transitions belonging to the n2 band.
(O - C)% = 6.1 (Toth) and 5.5 (This work)
Building a data base
Using the results of both analyses, a
data base was built and the spectrum
of the n2 band was computed.
Calculated
Observed
Observed
Calculated
Adding 0.3 Torr
of H216O
Line position analysis results:
microwave transitions
5591 data points. s = 1.7