Mid-IR Absorption Cross-Sections for Acetone PRESENTATION BY: RUQAYYAH F. ASKAR.
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Transcript of Mid-IR Absorption Cross-Sections for Acetone PRESENTATION BY: RUQAYYAH F. ASKAR.
Introduction Acetone: - Most of acetone released to the environment is of industrial origin.
- Acetone may pose a significant risk of oxygen depletion in aquatic systems due to microbial consumption.
- Acetone has a short lifetime estimated to be between two and four weeks.
- Acetone budget is poorly constrained.
Experimental Procedure Spectral region: 830 -1950
Spectrometer: High Resolution FTIR Spectrometer
To improve absorption path-length: Multi-pass cell with maximum optical path-length 19.3 m
[1]
Results and Conclusion Spectra of mixtures of acetone with dry synthetic air were recorded at 0.015
Spectra recorded at temperatures between 194 – 251 and atmospheric pressure.
Intensities were calibrated using three acetone spectra ( recorded at 278, 293, and 323 ) from PNNL infrared database.
New absorption cross-sections are combines with previous high resolution results -> to create a more complete set appropriate for remote sensing.
These cross-sections will provide an accurate basis for atmospheric retrievals of acetone in the mid-infrared spectral region.
Due to pressure sensitivity of acetone vapor pressure at low temperatures, the amount of absorber in the path-length was relatively uncertain. So, the y-axes of cross sections were calibrated using acetone spectra from the PNNL IR Database.
Results and Conclusion Continues
Spectral absorption cross sections, with units , were calculated by the equation:
Normalization requirements:
[1]
Results and Conclusion Continues
Acetone absorption cross sections at three different pressures to show the pressure dependence of the sharp structure: [1]
Results and Conclusion Continues
Other compounds for which absorption cross-sections were studied by the same group with similar approach:
Acetonitrile (: - Majority of emission arise from biomass burning
- High resolution cross-sections determined between 880 – 1700
Methanol (): - Highly toxic to humans, causing blindness and might lead to death.
- High resolution cross-sections determined in the 3.4 and 10 µm regions
Pacific Northwest National Lab. (PNNL)
Spectral coverage: 600 -6500 which corresponds to 16.16 – 1.53 .
Composite spectra: based on Beer’s low fit of 5 or more burdens.
Temperature: m.
All spectra include: full documentation and vapor pressure versus temperature curves.
[2]
Pacific Northwest National Lab. (PNNL) Continues
[2]
Growing list: over 400 compounds planned.
Database emphasis: reactive compounds, industrial pollutants, DOE fossil and nuclear fuel remediation species.
Sources [1] Jeremy Harrison, Neil Humpage, Nicholas Allen, Alison Waterfall, Peter Bernath, and John Remedios, Journal of Quantitative Spectroscopy and Radiative Transfer 112 (2011) 457-564.
[2] Northwest Infrared, Vapor Phase infrared Spectral Library, www.pnl.gov, April 30, 2015.
[3]Steven Sharp, T. Johnson, R. Sams, P. Chu, G. Rhoderick, and P. Johnson, “Gas Phase Databases for Quantitative infrared Spectroscopy”, Society for Applied Spectroscopy, V 58, 12 (2004).
[4]P.O.Wennberg, T. F. Hanisco, L. Jaegle, D. J. Jacob, E. J. Lanzendorf, et al, “Hydrogen radicals, nitrogen radicals and the production of in the upper tropodphere”, Science 279, 49 – 53 (1998).