Electrodynamic trapping, manipulation, and Raman characterization of single particles and fine particulate clouds

Elastic and inelastic light scattering measurements were used to examine the effect of particle morphology on Raman signals from suspended micrometer-sized particles. Single charged particles were trapped in an electrodynamic balance (EDB) and illuminated using a high power visible laser. Elastic scattering data were used to help interpret Raman signals obtained from binary solution droplets and particles undergoing chemical reaction with a component in the gas phase. Results from evaporation experiments on two-component hydrocarbon droplets show that Raman signals are enhanced when optical resonance occurs. Extended light scattering theory explains these effects. Results from reaction studies between sulfur dioxide gas and particles of alkali-metal hydroxides show that the reaction products are largely dependent upon the water content and phase of the particle.; After exploring the effect of particle morphology on Raman signals using single particles, an apparatus capable of trapping ensembles of particles was constructed where the mass and charge of the particles could be controlled with reasonable precision. Well-ordered arrays of particles were trapped of any number of particles up to 26. It was found that arrays could be compressed using a dc bias potential on the double-ring electrodes of the EDB. This compression technique was used to place more than one particle in the Raman scattering volume thereby improving the detection limit.; Particle arrays were further exploited to characterize the electric field of the EDB and to study particle-particle-gas chemical reactions. Using two-particle arrays, the ac and dc fields of a double-ring EDB were characterized completely and independently for the first time. Results were compared to existing electric field theories and to marginal stability analysis. Two oppositely charged particles were suspended apart using a dc separation potential, and the particles were then allowed to collide, which resulted in chemical reaction with water in the gas phase.; Finally, particle clouds were examined by trapping particles from a free, uncharged source aerosol. As particle size decreases it is increasingly difficult to charge particles adequately for trapping. This results in a trapping limit in the continuum regime. This limit was measured for a model aerosol, and the theoretical limit was estimated by examining the dynamic motion of particles in a time-dependent electric field.