ANALYSIS OF MICROMETER AND SUBMICROMETER ATMOSPHERIC AEROSOLS

THE USE OF MICRORAMAN SPECTROMETRIC TECHNIQUES SHOULD ALLOW THE COMPLETE MOLECULAR ANALYSIS OF A COLLECTED AEROSOL AS SMALL AS 0.1 MICROMETER IN DIAMETER. THIS WILL PROVIDE A TECHNIQUE FOR ANALYZING THE SMALL PARTICLES WHICH ARE KEY TO UNDERSTANDING ATMOSPHERIC CHEMISTRY. THE ULTIMATE GOAL OF THE PRESENT PROGRAM IS A PRACTICAL SPECTROMETER DESIGN WHICH CAN BE IMPLEMENTED (PHASE II) USING AVAILABLE HARDWARE AND EXISTING TECHNOLOGY. THE INITIAL PART OF THIS RESEARCH FOCUSES ON THE CHARACTERISTICS OF LIGHT SCATTERING SPECTRA FROM SAMPLES THAT ARE SMALLER THAN THE WAVELENGTH OF THE EXCITING LIGHT AS WELL AS THE PROBLEMS OF HANDLING, LOCATING AND PLACING THESE SMALL AEROSOLS, WHICH ARE NEITHER VISIBLE OR OBSERVABLE FROM THEIR REFLECTED LIGHT, IN THE MICRORAMAN SPECTROMETER. OTHER CONSIDERATIONS IN THE SPECTROSCOPY OF SMALL PARTICLES ARE THERMAL AND PHOTOCHEMICAL DEGRADATION. ONCE THESE HAVE BEEN ADDRESSED, THEN INSTRUMENTATION DESIGNS MUST BE CONSIDERED. THE EMPHASIS WILL BE PLACED ON THE FOLLOWING AREAS: GENERATING SUFFICIENT RAMAN PHOTONS, WHILE MAINTAINING SAMPLE INTEGRITY; COLLECTING THESE WITH EXCEPTIONALLY HIGH EFFICIENCY; AND THEN USING THEM PROPERLY. BASED ON THE INFORMATION GLEANED AND THE PROJECTED SPECTROMETER DESIGN, ANALYTICAL INFORMATION ON PARTICLE SIZE VS. THE AMOUNT OF SINGLE SPECIES NEEDED FOR DETECTION AND/OR QUANTIFICATION WILL BE DEVELOPED.