It has been thirty years since one of the authors (EJD) began a collaboration with Professor Milton Kerker at Clarkson University in Potsdam, New York using light scattering methods to study aerosol processes. The development of a relatively short-lived commercial particle levitator based on a modification of the Millikan oil drop experiment attracted their attention and led the author to the study of single droplets and solid microparticles by levitation methods. The early work on measurements of droplet evaporation rates using light scattering techniques to determine the size slowly expanded and diversified as better instrumentation was developed, and faster computers made it possible to perform Mie theory light scattering calculations with ease. Several milestones can be identified in the progress of single microparticle studies. The first is the introduction of the electrodynamic balance, which provided more robust trapping of a particle. The electrodynamic levitator, which has played an important role in atomic and molecular ion spectroscopy, leading to the Nobel Prize in Physics in 1989 shared by Wolfgang Paul of Bonn University and Hans Dehmelt of the University of Washington, was easily adapted to trap microparticles. Simultaneously, improvements in detectors for acquiring and storing light scattering data and theoretical and experimental studies of the interesting optical properties of microspheres, especially the work on morphology dependent resonances by Arthur Ashkin at the Bell Laboratories, Richard Chang, from Yale University, and Tony Campillo from the Naval Research Laboratories in Washington D. C.

Inhaltsangabe1 Background.- 1.1 Introduction.- 1.2 Light Scattering.- 1.2.1 Tyndall's Observations.- 1.2.2 Rayleigh Scattering.- 1.2.3 Lorenz-Mie-Debye Theory.- 1.2.4 Inelastic Scattering.- 1.2.5 Quasi-Elastic Scattering.- 1.3 Microparticle Transport Phenomena.- 1.3.1 Kinetic Theory.- 1.3.2 Continuum Theory.- 1.4 Transport in the Transition Regime.- 1.4.1 Transition Regime Mass Transfer.- 1.4.2 Transition Regime Heat Transfer.- 1.4.3 The Cunningham Correction.- 1.5 Particle Charge.- 1.5.1 The Cavendish Laboratory Experiments.- 1.5.2 Millikan's Experiments.- 1.6 Applications and Adaptations of MODE.- 1.6.1 Brownian Motion in Gases.- 1.6.2 Microdroplet Evaporation.- 1.6.3 Knudsen Aerosol Evaporation.- 1.6.4 A Kinetic Theory Approximation.- 1.6.5 Light Scattering Measurements.- 1.7 Particle Levitation Instrumentation.- 1.7.1 Magnetic Suspension.- 1.7.2 Electrostatic Suspension.- 1.7.3 Electrodynamic Suspension.- 1.7.4 Optical Levitation.- 1.7.5 Acoustic Levitation.- 1.8 The Vibrating Orifice Generator.- 1.9 Applications of Single Particle Devices.- 1.9.1 Concentrated Electrolyte Solutions.- 1.9.2 Microparticle Spectroscopies.- 1.9.3 Gas/Particle Chemical Reactions.- 1.9.4 Evaporation/Condensation Processes.- 1.9.5 Physical and Interfacial Properties of Microparticles.- 1.10 References.- 2 Particle Levitation.- 2.1 Introduction to Levitation Phenomena.- 2.2 Electrostatic Balances.- 2.3 Electrodynamic Balances.- 2.4 Principles of Electrodynamic Trapping.- 2.4.1 The Equation of Particle Motion.- 2.4.2 Trapping in a Potential Well.- 2.5 EDB Electric Fields.- 2.5.1 Spherical Harmonics Solution.- 2.5.2 Ring Charge Simulation.- 2.5.3 Electrode Asymmetries.- 2.5.4 Optimum Balance Shapes.- 2.6 Particle Stability in an EDB.- 2.6.1 The Ion Trap.- 2.6.2 The Microparticle Trap.- 2.6.3 Müller's Solution.- 2.6.4 Continued Fractions.- 2.6.5 Numerical Solutions.- 2.7 Nonhyperboloidal Balances.- 2.7.1 The Single Ring.- 2.7.2 Straubel's Three Disk Balance.- 2.8 Optical Levitation.- 2.8.1 The Optical Levitator.- 2.8.2 The Single-Beam Gradient Force Trap.- 2.9 Acoustic Levitation.- 2.9.1 Acoustic Pressure.- 2.9.2 The Barotropic Fluid.- 2.9.3 Energy Density of an Acoustic Wave.- 2.9.4 Acoustic Pressure on a Sphere.- 2.9.5 Particle Velocity and Phase Shift.- 2.9.6 Acoustic Levitators.- 2.9.7 Acoustic Measurements.- 2.10 References.- 3 Elastic Light Scattering.- 3.1 Introduction.- 3.2 Maxwell Equations.- 3.2.1 Constitutive Relations.- 3.2.2 Time-Harmonic Fields.- 3.2.3 Power and Energy Density.- 3.2.4 Polarization.- 3.3 Dipole Radiation.- 3.4 Cross Sections and Radiation Pressure.- 3.4.1 Cross Sections and Efficiencies.- 3.4.2 Radiation Pressure.- 3.4.3 Radiation Pressure Measurement.- 3.5 Rayleigh Scattering.- 3.5.1 Irradiance of Scattered Light.- 3.5.2 Polarization of the Scattered Light.- 3.6 Electromagnetic Theory.- 3.6.1 Multipole Expansion.- 3.6.2 Lorenz-MieTheory.- 3.6.3 Cross Sections and Efficiencies.- 3.6.4 Angular Scattering.- 3.6.5 Morphology-Dependent Resonances.- 3.6.6 Polarization Ratio.- 3.6.7 Electromagnetic Energy Absorption.- 3.6.8 Coated Spheres.- 3.7 Coupled Dipole Theory.- 3.8 Generalized Lorenz-Mie Theory.- 3.9 The T-matrix Method.- 3.10 Geometrical Optics.- 3.10.1 Basic Laws of Geometrical Optics.- 3.10.2 Interfaces.- 3.10.3 Transmitted and Scattered Fields.- 3.10.4 Optics of the Rainbow.- 3.11 Resonances.- 3.11.1 The Localization Principle.- 3.11.2 Resonance Conditions.- 3.11.3 Resonance Condition for Spherical Geometry.- 3.11.4 Quality factor Q and Line Width.- 3.12 References.- 4 Basic Single Particle Measurements.- 4.1 Force Measurement.- 4.2 Aerodynamic Drag.- 4.3 Levitation Characteristics.- 4.3.1 Direct Measurement of Co.- 4.3.2 Stability Measurements.- 4.3.3 SHEL Data.- 4.3.4 Double-Ring Measurements.- 4.3.5 Multiple Particle Trapping.- 4.4 Radiometric and Phoretic Forces.- 4.4.1 Radiation Pressure Force.- 4.4.2 Optical Trap Measurement.- 4.4.3 Phoretic Forces.- 4.4.4 Photophoresis Measurements.- 4.4.5 Thermophoresis Measurements.- 4.

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