Towards Greater Sensitivity: A Brief FTIR and Infrared-Based Cavity Ring Down Spectroscopy Comparative Study

A presentation of work comparing efficacy of a traditional IR method used as a standard within the U.S. Army Combat Capabilities Development Command (DEVCOM) and by international collaborators with that of an emerging technology, cavity ring down spectroscopy (CRDS).

Army Combat Capabilities Development Command, Aberdeen Proving Ground, MD

A threat in the form of chemical vapor may not be visible, but rapid detection is critical for preservation of life and property. In addition, understanding the surrounding environment informs the posture that the warfighter will need to take. The field of chemical vapor detection spans far beyond the warfighter and is rich in research. A search in SciFinder for “chemical vapor detection” provides over 400,000 results with over 3,000 books, 26,000 reviews, and nearly 300,000 journal articles. The focus of this document will be with an eye towards perimeter monitoring for a wide range of gas-phase chemicals. To accomplish such sensing, compound-specific sensors should not be employed as they lack capability to detect or inform about the presence of many potential threats outside of their selected targets. A viable technique for sensing a wide range of compounds is infrared absorption as most potential threats provide an infrared absorbance spectrum which arises from each compound's unique molecular structure.

The purpose of this article is to provide a comparison between a commercially available instrument long utilized as a standard within several defense laboratories around the globe which employs FTIR methods for detection of environmental gasses in industrial environments to a newer class of IR absorption-based detectors that use cavity ringdown to determine the absorption profile.