Mid-IR Absorption Cross-Sections for

AcetonePRESENTATION BY: RUQAYYAH F. ASKAR

Outline Introduction

Experimental Procedure

Results and Conclusion

PNNL IR database

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).