MICROPARTICLE ANALYSIS BY LASER SPECTROSCOPY*
Ignatius N. Tang and K. Hang Fung
Many areas of scientific research and technological development pertaining to DOE's missions demand chemical characterization of aerosol particles so minute in size that conventional methods for bulk analysis are simply not applicable. This program focuses specifically on basic understanding and novel application of laser-based spectroscopic methods for in situ characterization of such suspended microparticles. Because of the nondestructive and species-specific nature of Raman scattering, a unique single-particle Raman-spectroscopy method is currently being developed for composition analysis of microparticles. Progress has been made in establishing the detection limits for various Raman processes on microparticles. Sensitivity enhancement by resonance Raman scattering is being investigated. In addition, the single-particle levitation technique, in conjunction with spectroscopic tools to probe the physical and chemical state of molecular and ionic species in microparticles, is ideally suited for obtaining insight into the nature of ionic association and solute phase transformation at high concentrations otherwise unattainable in bulk solutions. Thus, discoveries have been made of new solid metastable states that exist only in microparticles, but not in the bulk phase. This research will not only provide the scientific and technological basis for advanced analytical instrumentation, but also lead to a discovery and elucidation of heretofore unknown properties unique to microparticles, thereby extending the frontier of material and catalyst research.
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*This work is supported by the Office of Energy Research, Office of Basic Energy Sciences, Chemical Sciences Division, Process and Techniques Branch, U.S. Department of Energy. (KC-03-02-02)