new high-resolution absorption cross-section measurements of hcfc-142b in the mid-ir karine le bris...
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![Page 1: New High-Resolution Absorption Cross-Section Measurements of HCFC-142b in the Mid-IR Karine Le Bris St Francis Xavier University, Nova Scotia, Canada Kimberly](https://reader030.vdocuments.site/reader030/viewer/2022032806/56649efb5503460f94c0e47f/html5/thumbnails/1.jpg)
New High-Resolution Absorption Cross-Section Measurements of
HCFC-142b in the Mid-IR Karine Le BrisSt Francis Xavier University, Nova Scotia, Canada
Kimberly StrongUniversity of Toronto, Ontario, Canada
Stella Melo Canadian Space Agency, Québec, Canada
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HCFC-142b in the atmosphereHCFC-142b (CF2Cl-CH3) is a substitute to CFC-11
ODP = 0.065
GWP = 1800 for an horizon of 100 yearsComplete phase-out scheduled for 2030
HCFC-142b annual global mean mole fractions from Oram et al., 1995, (blue), the AGAGE (green) and NOAA/ESRL (red) networks (O’Doherty et al., 2004; Montzka et al., 1999). From the Scientific Assessment of Ozone Depletion: 2006
Observed from space by the Canadian Atmospheric Chemistry Experiment (ACE) on the SCISAT-1 satellite mission.
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Aim
Improve the available data by acquisition of new Fourier Transform IR spectroscopy spectra at higher resolution (0.02 cm-1) and a larger set of temperature (223K-283K).
Evaluate the evolution of the integrated cross sections with temperature.
Compare experimental results to theoretical values obtained by density functional theory.
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Experimental conditions FTS: Bomem DA8.002, 250 cm maximum
optical path difference Source: Globar, Beamsplitter: KBr,
Detector: MCT Pressure measurement: MKS baratrons Temperature measurement: Omega
ungrounded thermocouple inserted into the cell
Chiller: Nestlab ULT-80 with Syltherm XLT (200-533 K)
3.17-cm coolable cell with vacuum jacket
Elimination of the black body emission from the source aperture
Correction of the MCT detector non-linearity effect on the raw data
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Experimental considerations Spectral Range: 650 –3500 cm-1
Resolution: 0.02 cm-1
Temperature Range: 223K-283K
Pressures: 2 to 12 torr
Data processing Removal of point from
optically thin medium (z<0.1): increase the signal-to-noise ratio
Removal of points from optically thick medium (z>1.1): elimination of saturation effect
Extrapolation at 0-torr limit to eliminate collisional broadening on ro-vibrational transitions
Wavenumber(cm-1)
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Experimental considerations Spectral Range: 650 –3500 cm-1
Resolution: 0.02 cm-1
Temperature Range: 223K-283K
Pressures: 2 to 12 torr
Data processing Removal of point from
optically thin medium (z<0.1): increase the signal-to-noise ratio
Removal of points from optically thick medium (z>1.1): elimination of saturation effect
Extrapolation at 0-torr limit to eliminate collisional broadening on ro-vibrational transitions
Wavenumber(cm-1)
![Page 7: New High-Resolution Absorption Cross-Section Measurements of HCFC-142b in the Mid-IR Karine Le Bris St Francis Xavier University, Nova Scotia, Canada Kimberly](https://reader030.vdocuments.site/reader030/viewer/2022032806/56649efb5503460f94c0e47f/html5/thumbnails/7.jpg)
Survey spectrum
Assignment done by comparison with theoretical results obtained by DFT (B3LYP and B3PW91)
All the strong lines are inside the atmospheric windows and correspond to C-Cl or C-F vibrations modes.
CH3 str.
CH3 def.
CF2 str., C-C str.
C-Cl str., CF2 def.
C-C-Cl def.
CF2 str.
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Data validationTemperature (K) Absorption band This work PNNL
(277K)Newnham and Ballard, 1995
Clerbaux et al., 1993
Cappellani and Restelli, 1992
273 8 0.70 0.736 0.70 0.69 0.75
7, 15 2.42 2.5 2.56 2.51 2.45
6,5,14 6.91 7.05 7.06 7.11 7.12
4,3,13 0.64 0.63 0.61 0.64 0.62
253 8 0.68 0.69 0.68
7, 15 2.36 2.41 2.40
6,5,14 6.76 6.16 6.96
4,3,13 0.65 0.65 0.78
233 8 0.67 0.71 0.754
7, 15 2.35 2.302 2.507
6,5,14 6.92 6.187 7.377
4,3,13 0.61 0.625 0.643
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Data validationTemperature (K) Absorption band This work PNNL
(277K)Newnham and Ballard, 1995
Clerbaux et al., 1993
Cappellani and Restelli, 1992
273 8 0.70 0.736 0.70 0.69 0.75
7, 15 2.42 2.5 2.56 2.51 2.45
6,5,14 6.91 7.05 7.06 7.11 7.12
4,3,13 0.64 0.63 0.61 0.64 0.62
253 8 0.68 0.69 0.68
7, 15 2.36 2.41 2.40
6,5,14 6.76 6.16 6.96
4,3,13 0.65 0.65 0.78
233 8 0.67 0.71 0.754
7, 15 2.35 2.302 2.507
6,5,14 6.92 6.187 7.377
4,3,13 0.61 0.625 0.643
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Integrated strengths vs temperature
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Data validationTemperature (K) Absorption band This work PNNL
(277K)Newnham and Ballard, 1995
Clerbaux et al., 1993
Cappellani and Restelli, 1992
273 8 0.70 0.736 0.70 0.69 0.75
7, 15 2.42 2.5 2.56 2.51 2.45
6,5,14 6.91 7.05 7.06 7.11 7.12
4,3,13 0.64 0.63 0.61 0.64 0.62
253 8 0.68 0.69 0.68
7, 15 2.36 2.41 2.40
6,5,14 6.76 6.16 6.96
4,3,13 0.65 0.65 0.78
233 8 0.67 0.71 0.754
7, 15 2.35 2.302 2.507
6,5,14 6.92 6.187 7.377
4,3,13 0.61 0.625 0.643
![Page 12: New High-Resolution Absorption Cross-Section Measurements of HCFC-142b in the Mid-IR Karine Le Bris St Francis Xavier University, Nova Scotia, Canada Kimberly](https://reader030.vdocuments.site/reader030/viewer/2022032806/56649efb5503460f94c0e47f/html5/thumbnails/12.jpg)
Temperature dependency
Strong T- dependence of the line shapes. The difference can be as large as 93% for a temperature
decrease of 60 K .
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Comparison with DFT
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Conclusions New high resolution (0.02cm-1) cross section
measurements of HCFC-142b are now available in the range 223K-283K.
No variation of the integrated intensity strengths with temperature has been observed.
Good concordance between DFT calculation and experience.