Transcript Lyulin_13CH4_2v3-E-MMS-2010-final.ppt

Near-IR Methane: Tetradecad
Empirical Lower State Energies of 13CH4
at 1.66 μm using 296 K and 81 K Spectra
Oleg M. Lyulin,
Laboratory of Theoretical Spectroscopy, Institute of Atmospheric Optics, Siberian Branch,
Russian Academy of Sciences, 1, Akademicheskii Av. 634055 Tomsk
Samir Kassi, Alain Campargue
Laboratoire de de Spectrométrie Physique (associated with CNRS, UMR 5588),
Université Joseph Fourier de Grenoble, B.P. 87, 38402 Saint-Martin-d'Hères Cedex, France
Keeyoon Sung and Linda R. Brown
Jet Propulsion Laboratory, California Institute of Technology,
4800 Oak Grove Dr., Pasadena, CA 91109, U.S.A.
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METHANE
POLYADS
 Global fit

new
1.3 1.66
μm
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New GOSAT-2009 Methane Empirical List: 5550–6236 cm−1
A.V. Nikitin et al. JQSRT 2010 (on line)
1E-20
Line intensity (cm/molecule)
New GOSAT-2009 line list in HITRAN format
2ν3
HITRAN08
1E-21
Wavenumber range (cm-1)
5550–6236
1E-22
Minim. Intens. (cm/molec)
4 × 10-26
1E-23
Total number of lines
10917
Number of assigned lines
2918
Number of partly assigned lines
1576
Number of 13CH4 assigned lines
318
1E-24
1E-25
 Mostly from HITRAN 1992 
(~2600 lines with ~1200 E" from
Margolis 1991, 1992 )
1E-26
5600
Line intensity (cm/molecule)
1E-20
5700
5800
5900
6000
6100
6200
GOSAT
Experimental sources
1E-21
1E-22
Number of analyzed spectra
1E-23
Range of pressures (Torr)
Temperatures (K)
1E-24
1E-25
1E-26
5600
5700
5800
5900
6000
6100
6200
Path lengths (cm)
47
1.9-760
180, 240,
267, 296
8.75 & 2010.
Wavenumber
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Present study: new 13CH4 measurements
Line Parameters
Obtained
FTIR At Room
Temperature
Diff. Absorption
At 81 K
Positions
Precisions
5850  6150 cm-1
0.0001  0.0100
++ Intensities
1.3×10-21 to 4×10-25
± 1% ± 200%
3.8×10-21 to 2.9×10-26
± 3%  ± 50%
7.81×10-20
7.43×10-20
3481
1629
+
Precisions
(estimated)
++ Sum of intensities
Number of meas. lines
# of empirical E"
# unmatched cold lines
+
++
in cm-1
in cm/molecule
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58526124 cm-1
0.001 cm-1
1196
433
Best for lines separated by >
0.2 cm-1 from nearby features
with intensities > 4 ×10-24 .
Some failed to match because
of severe blending in the Room
Temperature spectra.
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13CH
4
at 1.66 μm: Experimental Details
Kitt Peak FTS JPL Bruker 125
Diff. Abs.
Light Source
Beam Splitter
Detector
Resolution (unapodized)
Quartz-halogen
CaF2
InSb
0.0109 cm-1
Tungsten lamp
CaF2
InSb
0.0056 cm-1
DFB laser diode
na
InGaAs
Doppler limited
Sample Pressure (Torr)
0.684
0.882
0.34, 1.3, 8.9
Enriched Gas Samples
Path length (cm)
13CH (>90%)
4
13CH (>99%)
4
13CH (>99%)
4
7300
1309
142
295.9
3600 – 6900
293.6
5700 – 6500
81
5852-6124
H2O at 1.9 µm
Kitt Peak FTS
FTS
Temperature (K)
Useable Bandpass (cm-1)
Calibration Standards
Calibration Factor
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0.999998123(33)
1.0000001013( 12)
varies
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Room temperature spectra of enriched 13CH4
between 5800 and 6200 cm-1
JPL Bruker 125 FTS
Press & path: 0.882 torr, 1309 cm
2ν3 (F2)
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Kitt Peak FTS
0.684 torr, 7300 cm
ν1 + ν3 (F2)?
ν2+ ν3+ ν4 (F2+..)
2ν3 (E)
4ν2 ?
2 ν2 + ν3 (F2+…)
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Curve fitting Retrievals of positions and intensities
using Voigt profiles: example with P6 of 2ν3
FTS at Room Temperature
With JPL retrieval software
Diff. absorption at 81 K
with Grenoble software
Input linelist for retrievals was obtained
from peak finding with additional lines entered by hand.
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Empirical lower state E'' and J''
from the Two Temperature (2T) method
S 0 T   S 0 T0 
↑
↑
Q T0   T0 
 
Q T   T 

Q T0 
 1
1 
exp   E  


Q T 
 kT kT0  

(1)
↑
3/ 2
 S v (T )T 3 / 2
ln  0
 S v (T0 )T0 3 / 2
 0
(2)

  E  1  1 



kT
kT
0



E  B0 J   J   1
(3)
(4)
► With Eqs. 1-3, the approximate lower state energy is computed
using the ratio of line strengths measured at 296 and 81 K.
► The corresponding empirical lower state J'' value is computed with Eq. 4
rounding to the nearest integer.
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Validation of empirical lower states using P6 of 2ν3
Position
(cm-1)
5920.7049
5920.7920
5920.8452
5920.8589
5920.9061
5920.9411
5921.0276
5921.0475
5921.0687
5921.1045
Line Strengths
(cm/mol×10-22)
81 K
296 K
0.00350
0.00237
0.0354
0.829
2.14
1.21
3.12
2.01
5.18
0.023
1.18
3.03
0.0229
0.0518
1.18
3.02
1.93
5.04
E" in cm-1
'MEAS.'
??
358.2
224.1
224.1
224.3
??
223.9
214.0
225.6
226.0
J" emp
THEORY
Lower
Quanta
J" C" n
219.923
219.925
219.930
7.80
6.06
6.06
6.06
6
6
6
E 1
F2 1
A2 1
219.947
219.925
219.951
219.955
6.06
5.91
6.08
6.09
6
6*
6
6
F2
F2
F1
A1
Very good agreement is seen for the known P6 assignments within this 2ν3 manifold.
► The star (*) marks a line that appears to be a forbidden.
► Two weak are not matched to corresponding partner; no lower state can be computed.
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2
1
1
1
Validation of empirical lower states using P,Q,R of 2ν3
Only 7 of 248 already known assignments
differ by more than one value of J".
Jemp
minus
JAssigned
(by Nikitin
et al. 2010)
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Examples of lower state J determinations
(RT = room temperature, LNT = cold)
Top:
Absorbance near 296 K
Bottom: Transmittance at 81 K
Labeled by observed E"
►The 2T method is a robust but
blind method that uses the
positions agreement as the only
criterion (d < 0.002 cm-1) to
pair transitions observed in
both the RT and LNT spectra.
► The method gives poor results
if features are too blended and
have inconsistent line positions
and/or intensities.
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Histograms of 13CH4 empirical J" values
from 5852 to 6124 cm-1
► plotteds in 0.2 steps
► lines positions were matched in
the room and cold data using a
criterion of 0.002 cm-1.
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► Upper : log (intensities) vs J"
► Lower : strong lines only
► Most strong lines have integers
values of J".
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Open circles: measured positions
Solid dots:
known assignments
(see colors in legend)
Symbol size: line strength
Vib syms
(strong, medium, weak)
The A, F, E labels on the left
are vibrational symmetries
of the tetradecad sub-levels.
The F2 Bands are IR active.
Medium size circles near 5851 cm-1
may be 1+ 3 (F2 component).
→
No low J lines seen near 5900 cm-1.
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Present vs Prior HITRAN for 13CH4 at 1.66 μm
► Prior to 2008, HITRAN
at 1.66 μm had less
than 200 lines identified
as 13CH4.
► Last revised in 1992 with
lines observed in normal
sample spectra Or from
reported line positions
with relative intensities
scaled to isotopic
abundance.
► This new study provides
over 3400 entries from
direct measurements, of
which ~1200 have E".
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CONCLUSION
These new linelists with empirical lower states energies
► Improve molecular databases for planetary remote sensing
► Provide empirical J values for future theoretical analyses
Future work needed
► Additional experimental efforts and theoretical analyses
to understand the whole tetradecad spectrum and
provide the reliable prediction of molecular line parameters
for remote sensing of planetary atmospheres.
The present study is one important step
toward this ultimate goal.
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Differential Absorption in Grenoble
Experimental arrangement for the absorption spectroscopy cooled by LN2.
OI: optical isolator, C:fiber coupler, L: lens, D: detector, LN: liquid nitrogen
(S. Kassi et al. Phys. Chem. Chem. Phys. 10 (2008) 4410–4419.)
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