Two laser aerosol particle mass spectrometry

Mass analysis of single aerosol particles can be a useful tool because aerosols play an important role in a wide range of scientific problems. It has been the goal of this research to learn more about the physical aspects of the mass analysis of single aerosol particles, and to apply this knowledge to the improvement of the technique. An additional goal has been to extend two laser single aerosol particle mass spectrometry to the study of condensed phase reactions.; Once construction on the instrument was completed, ionization in the condensed phase was investigated using liquid aniline particles. The major results of this study included measurement of the ionization threshold for liquid aniline droplets, measurement of the number of ions arising from the liquid particles, and evidence that plasma formation affects the mass spectra, specifically by shifting mass peaks in time of flight. Ion-molecule reactions concluded that mass spectral analysis of aerosols would be improved by using an IR laser to vaporize particles, followed by UV or VUV ionization of molecules within the resulting vapor plume. IR vaporization of particles prior to UV illumination eliminates problems that arise from ionization in the condensed phase.; The next task involved study of the IR radiation initiated evaporation dynamics of the liquid particles. The main accomplishment of this study was the development of a model based on the Maxwell-Boltzmann distribution of molecular speeds that can help estimate temperatures generated in plumes arising from vaporized particles. Other issues were also investigated, such as the influence of vaporization on molecular ion fragmentation patterns.; Finally, this experimental apparatus was used in the study of condensed phase decomposition reactions of energetic materials. For the initial studies, the test molecule of o-nitrotoluene was used because of its chemical similarity to 1,3,5-trinitrotoluene (TNT), and for the relative safety in its handling. IR laser induced decomposition was observed from this molecule at IR laser intensities higher than 1 x 108 W/cm2. Also, laser generated vacuum ultra-violet (VUV) single photon ionization was used for the first time in aerosol analysis.