Photoacoustic spectroscopy of pressure- and temperature- dependence in the O2 A-band

Cich, Matthew J.

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https://hdl.handle.net/2142/96890 Copy

Description

Title

Photoacoustic spectroscopy of pressure- and temperature- dependence in the O2 A-band

Author(s)

Cich, Matthew J.

Contributor(s)

• Okumura, Mitchio
• Drouin, Brian
• Miller, Charles
• Crawford, Timothy J.
• Hodges, Joseph T.
• Long, David A.
• Bray, Caitlin
• Hogan, Daniel
• Rupasinghe, Priyanka
• Bui, Thinh Quoc
• Stroscio, Gautam
• Lunny, Elizabeth M.

Issue Date

2017-06-19

Keyword(s)

Atmospheric science

Abstract

NASA's Orbiting Carbon Observatory missions OCO-2 and OCO-3 require spectroscopic parameterization of the Oxygen A-Band absorption (757-775 nm) with unprecedented precision, to deliver space-based measurements of CO$_{2}$ column densities with an accuracy of better than 0.1%. Furthermore, with the long satellite-based pathlengths, the strongest A-Band lines are saturated. Accurate retrievals of O$_{2}$ column densities thus require precise modeling of the line shape, including the wings several linewidths from line center. The line shape model must go beyond the Voigt profile to include higher order effects such as Dicke narrowing, speed dependence, line mixing (LM), and collision-induced absorption (CIA). High precision laboratory data targeting these effects must be taken._x000d_ Line mixing and collision induced absorption have proven to be especially problematic in satellite retrievals of O$_{2}$ column densities. LM and CIA are more prominent at lower temperatures and higher pressures. A temperature-stabilized photoacoustic spectrometer was therefore designed to study the temperature- and pressure-dependence of spectral line shapes at temperatures from 230-296 K and pressures up to 5 atm. Progress toward high resolution (2 MHz) measurements of the full A-Band will be presented. The observed lineshapes are analyzed with the Hartmann-Tran Profile (HTP), which incorporates LM and CIA , using the Labfit multispectrum fitting program, and the determination of LM and CIA effects will be presented._x000d_

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/96890

DOI

https://doi.org/10.15278/isms.2017.MJ10

Copyright and License Information

Copyright 2017 Matthew J. Cich

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