Optimization of open path Fourier transform infrared spectrometry

The concepts relevant to the design of a quantitatively accurate Open Path (OP) Fourier Transform Infrared (FT-IR) spectrometer is described in this dissertation. OP/FT-IR systems are useful for detection and quantitation of anthropogenic and natural sources of most air pollutants and greenhouse gases. OP/FT-IR systems are currently employed for the determination of indoor, automotive, and industrial emissions, as well as composition and the total flux estimation of gases emitted from sources such as volcanoes, coal mines, and oceans.; Current OP/FT-IR systems have been demonstrated to be quantitatively inaccurate. This is largely due to the nonlinear photometric response of the detector used in all current systems. Use of a photometrically accurate but much less sensitive detector has necessitated the development of a novel efficient optical configuration. In addition, parameters relevant to accurate determination of atmospheric species measured over the long pathlengths normally encountered using OP/FT-IR spectroscopy have been evaluated.; The photometric accuracy of a detector similar to that used in conventional OP/FT-IR systems, as well as the detector to be used in the proposed optimized OP/FT-IR spectrometer, have been evaluated. The detector employed in current systems was found to exhibit inherently nonlinear photometric behavior, as well as a substantial dependence on experimental conditions. The detector to be used in the optimized system produced a linear photometric response over all measurement conditions.; Three novel optical hardware elements have been developed and evaluated. Two were found to generate the type of optical performance required for the proposed OP/FT-IR design, and are an integral part of the system currently under development.