Theoretical work on the water monomer and dimer Matt Barber Jonathan Tennyson University College London matt@theory.phys.ucl.ac.uk December 2008.
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Theoretical work on thewater monomer and dimer
Matt BarberJonathan TennysonUniversity College London
matt@theory.phys.ucl.ac.uk
December 2008
Outline of work so far
Improvements to water line list Extended to cover 800-19,600 cm-1
New sources added
Partition function for water dimer Few energy levels filled at low temperatures Most dimers are in the ground vibrational state Rotational levels convergent up to 20K No useful published comparisons
Line lists for 11000-19500 cm-1
HITRAN Good reference for strong lines
BT2 R J Barber and Jonathan Tennyson, UCL Theoretical model with experimentally determined energy levels.
Retrofitted experimental spectra Tolchenov R, Tennyson J: "Water line parameters from refitted
spectra constrained by empiricalupper state levels: study of the 9500-14500 cm-1 region". JQSRT, 109(4), 559-568 (2008).
Grenoble data Very accurate measurements using cavity ring down spectroscopy Comparatively clean area for HITRAN lines
Sources available in 11000 cm-1 to 19000 cm-1 region
0
1
2
3
4
11000 12000 13000 14000 15000 16000 17000 18000 19000
Frequency / cm-1
GRENOBLE
IMPERIAL
HITRAN
BT2
Line lists for 750-7500 cm-1
Coudert The H216O molecule: Line position and line intensity analyses up to the second triad,
L.H. Coudert, G. Wagner, M. Birk, Yu.I. Baranov, W.J. Lafferty, J.-M. Flaud, JMS (preprint 2008)
Brussels-Reims Fourier transform measurements of water vapor line parameters in the 4200-
6600 cm-1 region, Jenouvrier, A; Daumont, L; Regalia-Jarlot, L, et al., JQSRT (105/2. pp 326-355, 2007)
Giessen Water vapor absorption line intensities in the 1900-6600 cm-1 region, Mikhailenko,
SN; Albert, KAK; Mellau, G, et al., JQSRT (109/16, pp2687-2696, 2008)
Grenoble Weak water absorption lines around 1.455 and 1.66 mu m by CW-CRDS,
Mikhailenko, SN; Le, W; Kassi, S, et al., JMS (244/2, pp170-178, 2007)
Sources available in 750 cm-1 to 7500 cm-1 region
0
1
2
3
4
0 1000 2000 3000 4000 5000 6000 7000 8000
Frequency / cm-1
GRENOBLE
COUDERT
GIESSEN
JENOUVRIER
HITRAN/SISAM/TOTH
BT2
BT2 compared with HITRAN
-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
-25 -24 -23 -22 -21 -20 -19 -18
log intensity
log r
atio
(B/H
)
Coudert compared with BT2
-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
-25 -24 -23 -22 -21 -20 -19 -18
log intensity
log ra
tio (B
/C)
Comparison of HITRAN and UCL line lists
0
4E-27
8E-27
1.2E-26
1.6E-26
2E-26
817 817.5 818 818.5 819 819.5 820 820.5 821 821.5 822
Frequency / cm-1
Inte
sity
/ cm
mol
-1
HITRAN
UCL
Dimer partition function at 20K
Only lowest vibrational state occupied Rotational states up to J=20 occupied Statistical weights g from Groenemboom et
al. G
16 Symmetry
Equation:
gJeTQ kT
Ehc
)12()(
0 5 10 15 20 25 30 35 40 45 500
250500750
100012501500175020002250250027503000325035003750
Differing numbers of states
4
3
2
1
T / K
Parti
tion
Sum
0 5 10 15 20 25 30 35 40 45 500
250500750
100012501500175020002250250027503000325035003750
Differing maxJ values
J<21
J<18
J<15
J<12
J<9
T/K
Parti
tion
Sum
Conclusion
Monomer linelist Now covering from Submit to BADC? Publish?
Dimer partition function Convergent at 20K Reasonable at 50K Need many more levels for room temperature No low temperature comparisons available
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