Spectral library sheds light on chemicals
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A chemical's "John Hancock" can give it away. Just as a person's signature is unique and a sure way to weed out imposters and arrive at the truth, a chemical's spectral signature is a trustworthy form of identification. And such revealing information is becoming ever more vital in a world where detection of toxic substances could save lives and the environment.
At Pacific Northwest National Laboratory researchers have, for the past three years, been funded by the Department of Energy's Office of Nonproliferation to study the light that is absorbed or emitted by certain vapor phase chemicals--and to tie those characteristics to a unique spectral signature that can be read by both active and passive sensor devices. The result of the work is the DOE-PNNL Infrared Spectral Library, which contains signatures of more than 300 vapor phase chemicals and is growing by about 75 per year. Some of the chemicals are the "dual use" variety that have legitimate uses in industry but also could be used to make weapons.
"This collection of signatures is viewed as the definitive reference set by many of the users," said Steven Sharpe, one of the PNNL researchers involved in the effort. "When we started, it was widely thought that there was a need for remote sensing technologies that would measure chemicals, as well as a reference library of spectral signatures. We lobbied strongly that PNNL should be the laboratory developing the library, as this is in line with capabilities we have."
The research is conducted in the William R. Wiley Environmental Molecular Sciences Laboratory, a cutting-edge DOE research facility located at PNNL. Sharpe says most of the equipment employed for the spectral measurements is commercially available but has been modified for the purposes of this research.
The uses of the library's information are diverse and, considering some of the key issues facing the world, very timely. For instance, the library data, coupled with a sensing device, can determine if a smokestack is belching harmful emissions. Public safety is another potential application. A number of terrorist groups and countries have turned nerve and blister agents and other substances into weapons that could be unleashed on an unsuspecting public and cause great physical harm to individuals. In such cases, the availability of effective detection technologies would be extremely useful in identifying or responding to threats.
The contents of the spectral library are available to the general public. Currently there are nearly 100 subscribers--many of them companies that use the data as part of their environmental monitoring activities. Sharpe indicated that the project should wrap up within the next two years, and by then the database will contain about 500 signatures.
Sharpe noted that one of the requirements of the library is that the information must be produced in a fashion that is compatible with current or future instrumentation. That will help ensure that the data is relevant years into the future.
The DOE-PNNL Infrared Spectral Library Web site is located at http://nwir.pnl.gov.