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Proceedings Paper

Directly measuring aerosol absorption using photothermal interferometry (PTI)
Author(s): Arthur J. Sedlacek
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Paper Abstract

The importance of elucidating the direct and indirect effects of aerosol radiative forcing is now recognized as a significant component of our global climate forecasting models that must be better understood and quantified. Of particular interest is that of aerosol forcing through the so-called "direct" effect of aerosol absorption and scattering. This forcing can be of a magnitude comparable to those induced by anthropogenically-released greenhouse gases, yet can be either the opposite sign [negative (cooling)] or same sign [positive (warming)]. However, despite focused work on this issue, significant discrepancies on aerosol absorption still exist between measurements inferred from remote sensing and those obtained by in situ techniques. This is due, in large part, to the simple fact that the scattering channel dominates aerosol extinction, and thereby, makes measurement of the absorption difficult. An alternative method to measuring aerosol absorption will be presented: measurement of the thermal dissipation of the spectrally absorbed energy through interferometry. The use of this coherent optical detection technique is particularly well suited to measuring the refractive index change that accompanies this energy transfer process. [1,2] This technique was even demonstrated towards measuring aerosol absorption in the mid-1980s [3]. Attractive features of this technique for measuring aerosol absorption include its insensitivity to aerosol scattering, its ability to conduct the measurement in situ, its inherent high sensitivity, and near real-time response. A discussion on the theoretical basis for this technique along with some preliminary data will be presented. Potential applications of this instrument to environmental security problems will also be discussed.

Paper Details

Date Published: 10 November 2005
PDF: 11 pages
Proc. SPIE 5994, Chemical and Biological Sensors for Industrial and Environmental Security, 599401 (10 November 2005); doi: 10.1117/12.630859
Show Author Affiliations
Arthur J. Sedlacek, Brookhaven National Lab. (United States)

Published in SPIE Proceedings Vol. 5994:
Chemical and Biological Sensors for Industrial and Environmental Security
Arthur J. Sedlacek; Steven D. Christesen; Roger J. Combs; Tuan Vo-Dinh, Editor(s)

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