Photoinduced nucleation: A novel tool for detecting molecules in air at ultra-low concentrations
- Department of Chemical Engineering, The Johns Hopkins University, Baltimore, Maryland 21218 (United States)
This paper describes the development of a novel detection method and the demonstration of its capability to detect substances at concentrations as small as a few parts per trillion. It is shown that photoinduced nucleation is not in itself a nucleation process; rather, supersaturated vapor condenses onto long-lasting clusters formed by chemical reaction of photo-excited molecules. The role of the supersaturated vapor is to increase the size of these photoproducts by condensation to a size readily detectable by light scattering. Furthermore, the measured nucleation rate variation with illumination wavelength exactly matches the substance's vapor-phase UV light absorption wavelength dependence, thus providing species identification. The ability to detect and identify molecules of substances at extremely low concentrations from ambient air is useful for detecting and monitoring pollutants, and for detecting explosives such as TNT. (c) 2000 American Institute of Physics.
- OSTI ID:
- 20216294
- Journal Information:
- Journal of Chemical Physics, Vol. 112, Issue 19; Other Information: PBD: 15 May 2000; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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