CHIRPED-PULSE FOURIER TRANSFORM MICROWAVE SPECTROSCOPY: A NEW TECHNIQUE FOR RAPID IDENTIFICATION OF CHEMICAL AGENTS

Abstract

We have developed a new broadband Chirped-Pulse Fourier Transform Microwave (CP-FTMW) spectrometer that allows the microwave spectrum in the 7.5-18.5 GHz range to be measured in a single data event. This technique produces a pure rotational spectrum that can be used for unambiguous identification of any species having a permanent electric dipole moment. CP-FTMW is a gas phase technique that is ideally suited for the detection of airborne chemical warfare agents (CWA) which must be detected in trace amounts (<10 ppm in air). The high resolution of the technique allows the identification of complex mixtures without the need for a preliminary separation step, such as gas chromatography, which significantly reduces analysis time. The technique is “blind” to major atmospheric components ( N 2, O 2, CO 2, H 2 O ) as they either do not posses a permanent dipole moment or do not absorb in the range of the spectrometer, thereby eliminating large background signals. In this paper we will present preliminary results that are focused on early detection of airborne CWA, including acquisition time, sensitivity limits, and sample handling requirements for several of these species.