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The Validation of Fourier-Transform Microwave Spectroscopy for Trace-Gas Analysis



Pamela M. Chu, R D. Suenram, Angela R. Hight Walker, R S. DaBell, George C. Rhoderick, Gerald T. Fraser


There is strong interest by regulatory agencies and automobile manufacturers, motivated in large part by increasingly stringent emission standards, for measurement tools capable of quantifying various hydrocarbons, oxygenated hydrocarbons, etc., in automobile exhausts in near real time with sensitivity comparable to presently used gas chromatographs, i.e. nmol/mol. Concentration measurements of the exhaust-gas composition also potentially provide feedback on the complex chemistry in the engine and exhaust system, which may be used to improve fuel formulations and engine performance and reduce emissions. Here, we describe the technique of Fourier-Transform MicroWave (FTMW) spectroscopy, which is a high sensitivity technique (better than mmol/mol, i.e. 1 ppm) with near real-time response (down to 1 s) and 100 % certain chemical identification. The development of FTMW for gas analysis builds upon a long history at NIST in the quantitative analysis of gas mixtures, which includes standard reference gas mixtures, and more recently the development of a quantitative infrared spectral database of common air pollutants (Chu et al., 1999).
NIST Interagency/Internal Report (NISTIR) -


analytical chemistry, automobile emissions, Fourier-transform microwave spectroscopy, microwave spectroscopy, molecular spectroscopy, trace-gas analysis


Chu, P. , Suenram, R. , Hight Walker, A. , DaBell, R. , Rhoderick, G. and Fraser, G. (2002), The Validation of Fourier-Transform Microwave Spectroscopy for Trace-Gas Analysis, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD (Accessed June 21, 2024)


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Created January 31, 2002, Updated October 12, 2021