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Proceedings Paper

Fourier transform molecular rotational resonance spectroscopy for reprogrammable chemical sensing
Author(s): Brent J. Harris; Robin L. Pulliam; Justin L. Neill; Matt T. Muckle; Roger Reynolds; Brooks H. Pate
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Paper Abstract

Molecular rotational resonance (MRR) spectroscopy gives spectral signatures with high chemical selectivity. At room temperature, the peak intensity of the MRR spectrum occurs in the 100 GHz – 1 THz frequency range for volatile species with mass ≤ 100 amu. Advances in high-power sub-mm-wave light sources has made it possible to implement time-domain Fourier transform (FT) spectroscopy techniques that are similar to FT nuclear magnetic resonance (FT-NMR) measurements. In these measurements, the gas sample is excited by a short (200 ns) excitation pulse that creates a macroscopic sample polarization. The electric field of the subsequent transient molecular emission is detected using a heterodyne receiver and a high-speed digitizer. FT-MRR spectroscopy offers speed and sensitivity improvements over absorption spectroscopy. For chemical analysis, FT-MRR spectrometers combine the benefits of broad chemical coverage typical of gas chromatography – mass spectrometry (GC-MS) instruments and the direct measurement capabilities of infrared gas sensors all in a reprogrammable platform. Pulse sequence measurements can be implemented for advanced spectroscopic analysis. Trace level quantitation of volatile species at ppbv concentration can be performed on the time scale of a minute. In cases where the sample is a complex mixture, a double-resonance pulse sequence can be used to achieve chemical selectivity even in cases where spectral overlap occurs. These measurement capabilities are illustrated using the application of FT-MRR spectroscopy to residual solvent analysis of pharmaceutical products.

Paper Details

Date Published: 14 March 2015
PDF: 10 pages
Proc. SPIE 9362, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications VIII, 936215 (14 March 2015); doi: 10.1117/12.2080101
Show Author Affiliations
Brent J. Harris, BrightSpec, Inc. (United States)
Robin L. Pulliam, BrightSpec, Inc. (United States)
Justin L. Neill, BrightSpec, Inc. (United States)
Matt T. Muckle, BrightSpec, Inc. (United States)
Roger Reynolds, BrightSpec, Inc. (United States)
Brooks H. Pate, BrightSpec Inc. (United States)
Univ. of Virginia (United States)


Published in SPIE Proceedings Vol. 9362:
Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications VIII
Laurence P. Sadwick; Tianxin Yang, Editor(s)

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