DETERMINATION OF PRESSURE
BROADENING AND SHIFTS FOR THE
FIRST OVERTONE
2←0 OF HCL
Brennan M. Coffey, Brian J. Drouin,
Timothy J. Crawford
Jet Propulsion Laboratory, California
Institute of Technology
6/16/2014
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Motivation
• Textbook case
– but precision is not up to modern standards
– Last Investigation into the line centers of HCl in the MIR was done by
Guelachvili Opt. Comm. 19(1) 150-154, 1976 line positions to ~2x10-4 cm-1
• Laboratory calibration
– Wavenumber calibration for 6000 cm-1 region
– Dual scan experiment has allowed transfer of CH4 standard to HCl
– Positions may be improved to ~1x10-5 cm-1
• No (bandwide) self broadening or self shift parameters
– TCCON calibration, common calibration for networked measurement system
– Remote sensing for Venusian / Jovian / Saturnian chemistry
• LabFit exercise
– Multispectrum lineshape fitting
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Band Selection
http://hitran.iao.ru/survey/spectr
4800
5200
5600
6000
cm -1
Pubchem
commons.wikimedia.org
halo.wikia.com
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3
TCCON network
•
•
•
•
The Total Carbon Column Observing Network
(TCCON) is a network of ground-based
Fourier Transform Spectrometers that record
direct solar spectra in the near-infrared.
From these spectra, accurate and precise
column-averaged abundances of
atmospheric constituents including CO2, CH4,
N2O, HF, CO, H2O, and HDO, are retrieved.
Calibrations are performed with sealed 10
cm 5mb HCl cells inside each interferometer
Hase, F., B.J. Drouin, C.M. Roehl, G.C. Toon,
P.O. Wennberg, D. Wunch, T. Blumenstock, F.
Desmet, D.G. Feist, P. Heikkinen, M. De
Maziere, M. Rettinger, J. Robinson, M.
Schneider, V. Sherlock, R. Sussmann, Y. Te, T.
Warneke, C. Weinzierl, Calibration of sealed
HCl cells used for TCCON instrumental line
shape monitoring, Atmos. Meas. Tech. 6(12),
3527-3537, 2013.
‘Narrowing’ effect is evident in Hase et al.
6/16/2014
http://www.tccon.caltech.edu/site-locations/index.html
https://tccon-wiki.caltech.edu/
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Remote Sensing of HCl
Goto et al.
Earth Science:
HALOE, ACE, MLS, Odin, ATMOS
Mk IV, FIRS-2, SLS, (ALIAS in-situ)
Venus, solar occultation spectra,
http://venus.aeronomie.be/en/soir/hcl.htm
Also astronomy with:
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Spitzer,
ISO, ATMOS, Odin, Herschel MK10 HCl Overtone Lineshapes
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IFS125HR
Pressure scans
in a joint
tandem cell at 8
different
pressures
Bruker IFS-125HR at JPL
▪ The entire FTS enclousure evacuated to ~10 mTorr
▪ Maximum resolution, 0.0011 cm-1
▪ Detectors and beamsplitters covering 20 - 15800 cm-1
▪ Gas handling system with a 6″ Varian Turbo pump
▪ MKS Baratron pressure gauges up to 6.5 bar
▪ Hart Scientific PRT temperature sensors
Various absorption gas cells
▪ Multipass White cell of (variable path length up to 32.5 m)
▪ Cryogenic cell (0.2 m long, developed by Dr. Arlan Mantz)
▪ Various single pass custom cells (from 2 cm to 26.5 cm)
▪ Very long path multipass White cell (~200 m) on the way
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Experimental
• Two cells were used
• Long Path length (3.84 m)
• Short Path length
(0.0614 m and 0.1526 m)
(This goes inside the FTS)
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Calibration strategy
• Recent improvements in the metrology of CH4 and C2H2 have made the
desired precision and accuracy attainable
• Absolute positions were determined with femtosecond laser spectroscopy
Zolot, 2013
Zolot et al. JQSRT 118 (2013) 26-39
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σ (MHz)
σ (cm )
2.3
7.6E-05
1.0
3.3E-05
1.7
5.6E-05
2.5
8.3E-05
2.4
8.0E-05
1.2
4.0E-05
7.8
2.6E-04
1.3
4.3E-05
0.5
1.6E-05
1.2
4.0E-05
1.5
5.0E-05
0.8
2.6E-05
…
…
-1
8
•
Position
Algorithm Information
– Code in Matlab was written to analyze the spectra for line centers
– Thresholding based on a ratio of intensity at the base of the peak and intensity at the
peak was used as filtering criteria
• <5% of max intensity was not considered a peak
– Peak picker uses zero filling, apodization, then spline interpolation between the bottom
3 points
– Peak minimum finder based on 5 smoothing points and first and second derivative tests
6100
6080
6060
y = 0.9999984244x
Standard CH
4
Residuals (cm-1)
6040
6020
6000
5980
5960
5940
5920
5900
5900
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Position
(cm-1)
5920
MK10 HCl Overtone Lineshapes
5940
5960
5980
6000
6020
Empirical CH
4
6040
6060
6080
6100
9
Line Centers
Number Matched
Match Threshold
Standard Deviation
Cal Factor
46
0.00221
0.00007009
1.00000093
40
0.00057
0.00003566
1.00000010
20
0.00012
0.00001120
1.00000003
8
0.00010
0.00000819
1.00000009
• Matched values to the Zolot lines, goal was to improve the calibration error to
be <2x10-4 cm-1
• We can get 1x10-5 cm-1, sufficient precision and accuracy for use in OCO
spectral analyses
• Precision was verified with quantum mechanical prediction software and had
an RMS of ~7x10-6 cm-1
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Pressure Broadening
• 1st Pressure broadening
and pressure shifts for
entire v = 2-0 band
• Spectra taken in a dual
chamber cell were
used with CH4 in one
chamber as the
calibrant and HCl in the
other
• Pressures investigated
were 10,15, 20, 25, 30,
40, 50 and 60 Torr
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•
Spectral
Fitting
no
constraints
Full Physics fits with LabFit to get pressure broadening and pressure shift
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Fitting Spectra with constraints
Intensities with Honl-London Factors, exp(hv/kT), positions with B0,B2, D0,D2, H0, H2
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Linestrength – HITRAN
• On average 2.6%
higher than
HITRAN
• Both intensity and
pressure
broadening are
consistently higher
than HITRAN
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Isotopologues Comparison – Self
Broadening
self broadened halfwidth (cm-1/atm)
0.3
0.25
0.2
0.15
0.1
0.05
0
0
2
4
6
8
10
|m|
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0.035
0.035
0.03
0.03
0.025
0.025
self shift (cm-1/atm)
self shift (cm-1/atm)
Isotopologues Comparison – Self Shift
0.02
0.015
0.01
0.005
0.02
0.015
0.01
0.005
0
0
0
-0.005
2
4
6
|m|
8
10
-7
-5
-0.005
-3
-1
1
3
5
7
9
m
The self-shift is not reported in HITRAN, nor any literature, yet it is
critical to precisely calibrate the wavenumber of a spectrometer
using typical HCl absorption pressure-pathlengths.
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11
Isotopologues Comparison – Dicke
0.06
0.05
0.05
0.04
0.04
Dicke parameter
Dicke parameter
0.06
0.03
0.02
0.01
0.03
0.02
0.01
0
0
2
4
6
8
10
0
-7
|m|
-2
3
8
m
The narrowing phenomenon is correlated with instrument variables such as
resolution and aperture. The multispectrum fitting method allows a consistent
retrieval over many pressures with these instrument variables fixed. The
isotopologue comparison highlights the reproducible trend that has been separated
from instrument variables.
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Hamiltonian Parameters from
constrained fit
Guelachvili Opt. Comm. 19(1) 150-154, 1976
SQ/nu(H35Cl)
SQ/nu(H37Cl)
c1 (H35Cl)
c1 (H37Cl)
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0.10469429511D-23
0.33157419710D-24
-.22686827401D-02
-.22476757421D-02
G(H35Cl)
G(H37Cl)
B"(H35Cl)
B"(H37Cl)
D"(H35Cl)
D"(H37Cl)
H"(H35Cl)
H"(H37Cl)
B'(H35Cl)
B'(H37Cl)
D'(H35Cl)
D'(H37Cl)
H'(H35Cl)
H'(H37Cl)
0.11154688922E-27
0.57034946781E-28
0.10987143469E-04
0.21406525775E-04
MK10 HCl Overtone Lineshapes
5667.9824970
5663.9268346
10.440189334
10.424502872
0.52805708530D-03
0.52645439847D-03
0.16600000000D-07
0.22900000000D-07
9.8345885033D+01
9.8202784918D+01
0.51541494165D-03
0.51416332228D-03
0.15400000000D-07
0.21300000000D-07
0.31266838505E-05
0.57468641899E-05
0.47834078032E-06
0.10281972891E-05
0.12479988598E-07
0.39573635036E-07
Fixed
Fixed
0.43757773938E-06
0.10900827192E-05
0.87793443626E-08
0.29243450328E-07
Fixed
Fixed
C01 = -2.60(27)x10-3, c02 = -0.86(57)x10-3
Tipping & Ogilvie JMS. 96 442-450, 1982
Toth et al. JMS. 35, 110-126, 1970
18
Summary and Future Directions
• HCl spectra at multiple pressures have been
analyzed simultaneously for lineshape
parameters
• Low pressure scan has intensity issues, but
should improve accuracy of positions
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Acknowledgements
•
•
•
•
•
•
NASA ACLR
OCO-2 ABSCO
Linda Brown
Keeyoon Sung
Malathy Devi
D. Chris Benner
© 2014 California Institute of Technology.
Government sponsorship acknowledged.
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Pressure Broadening – HITRAN
H35Cl
m
H37Cl
Percent
Difference
Self Width HITRAN Self
from
Self Width
Error
Width
HITRAN
m
Percent
Difference
Self Width HITRAN Self
from
Self Width
Error
Width
HITRAN
-5
0.2088
0.0001
0.213
1.9336
-4
0.2323
0.0002
0.238
2.3542
-4
0.2346
0.0001
0.238
1.4042
-3
0.2420
0.0002
0.242
0.0041
-3
0.2439
0.0001
0.242
0.7758
-2
0.2350
0.0002
0.229
2.5926
-2
0.2366
0.0001
0.229
3.2751
-1
0.2178
0.0003
0.213
2.2151
-1
0.22
0.0001
0.213
3.2442
1
0.2109
0.0003
0.201
4.8610
1
0.2131
0.0001
0.201
5.9173
2
0.2229
0.0002
0.215
3.6072
2
0.2246
0.0001
0.215
4.3936
3
0.2277
0.0002
0.224
1.6368
3
0.2299
0.0001
0.224
2.6022
4
0.2200
0.0002
0.218
0.8793
4
0.2223
0.0001
0.218
1.9253
5
0.1994
0.0002
0.197
1.1825
5
0.2016
0.0001
0.197
2.2703
6
0.1733
0.0002
0.169
2.5010
6
0.1752
0.0001
0.169
3.6236
7
0.1469
0.0003
0.139
5.5937
7
0.1484
0.0001
0.139
6.6191
8
0.1254
0.0004
0.111
12.7785
8
9
0.1269
0.108
0.0001
0.0002
0.111
0.096
14.0537
12.2358
9
0.1082
0.0006
0.096
12.4713
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Linestrength
–
HITRAN
H Cl
H Cl
37
35
m
Intensity
HITRAN
intensity
Difference
percent
difference
m
-5
6.66E-21
6.38E-21
2.83E-22
4.44
-4
2.79E-21
2.69E-21
1.02E-22
3.79
-4
8.83E-21
8.44E-21
3.93E-22
4.66
-3
3.13E-21
3.02E-21
1.19E-22
3.93
-3
9.90E-21
9.46E-21
4.47E-22
4.73
-2
2.83E-21
2.72E-21
1.11E-22
4.08
-2
8.93E-21
8.53E-21
4.05E-22
4.74
-1
1.72E-21
1.66E-21
6.32E-23
3.81
-1
5.46E-21
5.21E-21
2.45E-22
4.71
1
1.90E-21
1.83E-21
7.17E-23
3.92
1
6.02E-21
5.75E-21
2.71E-22
4.71
2
3.44E-21
3.31E-21
1.36E-22
4.12
3
4.21E-21
4.05E-21
1.60E-22
3.94
4
4.14E-21
3.98E-21
1.56E-22
3.90
5
3.46E-21
3.32E-21
1.31E-22
3.95
6
2.50E-21
2.41E-21
8.77E-23
3.64
Intensity
HITRAN
intensity
Difference
percent
difference
2
1.09E-20
1.04E-20
4.84E-22
4.66
3
1.33E-20
1.27E-20
5.95E-22
4.69
4
1.31E-20
1.25E-20
5.78E-22
4.62
5
1.09E-20
1.04E-20
4.80E-22
4.61
6
7.90E-21
7.54E-21
3.54E-22
4.70
7
5.02E-21
4.80E-21
2.20E-22
4.59
7
1.59E-21
1.54E-21
5.39E-23
3.51
8
2.83E-21
2.71E-21
1.20E-22
4.42
8
8.96E-22
8.68E-22
2.83E-23
3.26
9
1.42E-21
1.37E-21
5.99E-23
4.39
9
4.55E-22
4.37E-22
1.81E-23
4.15
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Isotopologues Comparison – Line
strengths
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MK10 HCl Overtone Lineshapes
Point
Ratio
2
3.16
3
3.16
4
3.16
5
3.17
6
3.16
7
3.17
8
3.16
9
3.16
10
3.15
11
3.17
12
3.16
13
3.16
14
3.12
23