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Proceedings Paper

Experimental determination of terahertz atmospheric absorption parameters
Author(s): David M. Slocum; Thomas M. Goyette; Robert H. Giles; William E. Nixon
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Paper Abstract

The terahertz frequency regime is often used as the ‘chemical fingerprint’ region of the electromagnetic spectrum since many molecules exhibit a dense selection of rotational and vibrational transitions. Water is a major component of the atmosphere and since it has a large dipole moment the propagation of terahertz radiation will be dominated by atmospheric effects. This study will present the results of high-­‐resolution broadband measurements of the terahertz atmospheric absorption and detail the technique for directly measuring the pressure broadening coefficients, absolute absorption coefficients, line positions, and continuum effects. Differences between these measured parameters and those tabulated in HITRAN will be discussed. Once the water vapor absorption was characterized, the same technique was used to measure the line parameters for methanol, a trace gas of interest within Earth’s atmosphere. Methanol has a dense absorption spectrum in the terahertz frequency region and is an important molecule in fields such as environmental monitoring, security, and astrophysics. The data obtained in the present study will be of immediate use for the remote sensing community, as it is uncommon to measure this many independent parameters as well as to measure the absolute absorption of the transitions. Current models rely on tabulated databases of calculated values for the line parameters measured in this study. Differences between the measured data and those in the databases will be highlighted and discussed.

Paper Details

Date Published: 13 May 2015
PDF: 12 pages
Proc. SPIE 9483, Terahertz Physics, Devices, and Systems IX: Advanced Applications in Industry and Defense, 94830O (13 May 2015); doi: 10.1117/12.2176455
Show Author Affiliations
David M. Slocum, Univ. of Massachusetts Lowell (United States)
Thomas M. Goyette, Univ. of Massachusetts Lowell (United States)
Robert H. Giles, Univ. of Massachusetts Lowell (United States)
William E. Nixon, U.S. Army National Ground Intelligence Ctr. (United States)

Published in SPIE Proceedings Vol. 9483:
Terahertz Physics, Devices, and Systems IX: Advanced Applications in Industry and Defense
Mehdi F. Anwar; Thomas W. Crowe; Tariq Manzur, Editor(s)

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