The Airborne Microparticle: Its Physics, Chemistry, Optics, and Transport Phenomena

840 Pages·2002·20.28 MB·English

by  Prof. E. James Davis

E. James Davis • Gustav Schweiger
The Airborne Microparticle
Springer-Verlag Berlin Heidelberg GmbH
E. James Davis • Gustav Schweiger
The Airborne
Microparticle
Its Physics,
Chemistry,
Optics,
and Transport Phenomena
With 353 Figures
Prof. E. James Davis
University of Washington
Department of Chemical Engineering
Box 351750
Seattle, WA 98185-1750
USA
Prof. Dr. Gustav Schweiger
Ruhr-Universität-Bochum
Institut für Automatisierungstechnik
Lehrstuhl für Laseranwendungstechnik
und Meßsysteme, Maschinenbau
Universitätsstr. 150
44780 Bochum
Germany
e-mail: [email protected]
ISBN 978-3-642-62806-1
Library of Congress Cataloging-in-Publication Data
E. James Davis:
The Airborne Microparticle: Its Physics, Chemistry, Optics, and Transport Phenomena /
E. James Davis; G. Schweiger. - Berlin; Heidelberg; New York; Barcelona; Hong Kong; London;
Milan; Paris; Tokyo: Springer 2002
(Engineering online library)
ISBN 978-3-642-62806-1 ISBN 978-3-642-56152-8 (eBook)
DOI 10.1007/978-3-642-56152-8
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© Springer-Verlag Berlin Heidelberg 2002
Originally published by Springer-Verlag Berlin Heidelberg New York in 2002
Softcover reprint of the hardcover 1st edition 2002
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Foreword
It has been thirty yearssince one ofthe authors (EJD) began a collaboration with
ProfessorMilton Kerker atClarkson University inPotsdam, New York using light
scattering methods to study aerosol processes. The development of a relatively
short-lived commercial particle levitator based on a modification ofthe 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 withease.
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 ofa particle. The electrodynamic levitator, which
hasplayed an importantrole inatomic and molecularion spectroscopy, leading to
the Nobel Prize in Physics in 1989 shared by Wolfgang Paul ofBonn 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 propertiesofmicrospheres,especiallythework 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. provided additional tools for precise measurements of the
optical propertiesofspheresand spheroids. The work atthe Bell Laboratories also
led to the optical levitator and to the 'optical tweezers' for manipulating small
particles, including bacteria and other colloidal matter. A major milestone that
made it possible to study the chemistry of the microparticle was the combination
ofsingle particle levitation with inelastic scattering.This providedthe incentive to
move from the physics ofsmall particles to theirchemistryandchemical reactions
using Raman and fluorescence spectroscopies. The development of the vibrating
orifice aerosol generator at the University of Minnesota provided yet another tool
forprobing thesingleparticle inachain ofidentical particles.
With the range of theoretical and experimental tools available it has become
possible to use the many unique properties of droplets and small particles to
investigate phenomena as diverse as linear and nonlinear optics, solution
thermodynamics,gas/solid and gas/liquid chemical reactions, transport properties
VI Foreword
such asgas phase diffusion coefficients,rate processes inthecontinuumand non
continuum regimes, trace gas uptake by aerosol droplets related to atmospheric
chemistry and ozone depletion, phoretic phenomena, Raman spectroscopy, single
molecule identification (by fluorescence methods), the physics and chemistry of
bioaerosols, particle charge,evaporationandcondensation processes and others.
The happy collision of the authors came about because of their mutual interest
in elastic and inelastic light scattering from small particles when Professor
Schweiger was at the Gerhard-Mercator-Universitat in Duisburg, Germany, and
Professor Davis had moved to the University of Washington in Seattle. Their
interaction grew when Professor Schweiger accepted his position at the Ruhr
Universitat in Bochum where itbecame possible todevelop awide range of laser
based instrumentation for microparticle research. The authors are grateful that
their interaction was supported bythe Deutscher AkademischerAustausdienst and
the international cooperation program of the National Science Foundation (Grants
CTS-9528897 and INT-9725216).
One must give credit where it is due, and it isthe wonderful group of graduate
students and post-doctoral researchers that have made this book areality.It is not
reasonable to provide a list covering thirty years, but we must recognize the
contributionsof many ofour younger colleagues.First and foremost isour mutual
friend and colleague, Professor Asit K. Ray of the University of Kentucky. It was
he who brought to our attention the papers of Paul on the quadrupole and who
built the first such instrument for Professor Davis. His doctoral work earned him
the first Kenneth Whitby Award of the American Association for Aerosol
Research. That work was followed by Dr. Ravidran Perisasamy at Clarkson and
the University of New Mexico, Dr. Randolph Chang, Dr. Christopher Guzy,
Professor Timothy Ward of the University of New Mexico, Dr. Shu-Hua Zhang,
John Fulton, Dr. Daniel Taflin, Dr.Theresa M. Allen, Dr. Mark Buehler,Dr. Scot
Rassat, Dr. Willard Foss, Dr. Wanguang Li, Dr. Christopher Aardahl, Dr. John
Widmann, Research Professor Brian Swanson, Dr. Mary Laucks, Dr. Richard
Zheng andothers. Ontheother sideof theocean Dr.Reinhard Vehring, Dr.Cemal
Esen, Dr. Thomas Kaiser, Dr. GUnterRoll, Dr. Chao Liu, Dr. Bin Xu, Dr. Helge
Moritz, Dr. Jorg Schulte, Thomas Weigel and many students have contributed to
extend the knowledge of microparticles and their interaction with light and the
surroundinggas.
The comprehensiveness and rigor of the theoretical treatment were generally
sacrificed in favor of the presentation of the basic concepts. More space was
devoted totheory whenthe authors felt that noorfew comprehensivedescriptions
of the phenomena were available. Throughout this book the main concern of the
authors was to provide the reader with a visualization of the significance and
application of theory.To emphasize this point experimental results are presented
asfaraspossible.
Bochum, Seattle Gustav Schweiger
Spring 2002 James Davis
Contents
1Background 1
1.1Introduction 1
1.2Light Scattering .4
1.2.1Tyndall'sObservations .4
1.2.2RayleighScattering 6
1.2.3Lorenz-Mie-DebyeTheory 8
1.2.4 Inelastic Scattering 12
1.2.5Quasi-ElasticScattering 16
1.3MicroparticleTransportPhenomena 16
1.3.1Kinetic Theory 17
1.3.2ContinuumTheory 19
1.4TransportintheTransition Regime 22
1.4.1Transition Regime MassTransfer. 24
1.4.2 TransitionRegime HeatTransfer. 26
1.4.3The CunninghamCorrection 26
1.5Particle Charge 27
1.5.1The CavendishLaboratoryExperiments 28
1.5.2Millikan'sExperiments 30
1.6Applicationsand AdaptationsofMODE 32
1.6.1Brownian Motion inGases 33
1.6.2MicrodropletEvaporation 34
1.6.3 Knudsen Aerosol Evaporation .37
1.6.4A Kinetic Theory Approximation 39
1.6.5Light ScatteringMeasurements .40
1.7Particle LevitationInstrumentation .42
1.7.1 Magnetic Suspension .42
1.7.2Electrostatic Suspension .43
1.7.3Electrodynamic Suspension .44
1.7.4Optical Levitation .47
1.7.5Acoustic Levitation ..49
1.8The Vibrating Orifice Generator ..49
1.9ApplicationsofSingle ParticleDevices 50
1.9.1ConcentratedElectrolyteSolutions 51
1.9.2 Microparticle Spectroscopies 51
1.9.3GasIParticle ChemicalReactions .53
VIII Contents
1.9.4Evaporation/CondensationProcesses 54
1.9.5Physical andInterfacial Properties of
Microparticles 55
1.10References 57
2Particle Levitation 67
2.1 IntroductiontoLevitation Phenomena 67
2.2ElectrostaticBalances 69
2.3 ElectrodynamicBalances 71
2.4 PrinciplesofElectrodynamicTrapping 78
2.4.1The Equationof Particle Motion 78
2.4.2 Trapping inaPotential Well 79
2.5EDB Electric Fields 82
2.5.1Spherical HarmonicsSolution 84
2.5.2 Ring Charge Simulation 94
2.5.3ElectrodeAsymmetries 101
2.5.4 OptimumBalanceShapes 103
2.6Particle StabilityinanEDB 104
2.6.1The IonTrap 106
2.6.2The MicroparticleTrap 109
2.6.3 MUller's Solution 110
2.6.4ContinuedFractions 110
2.6.5 Numerical Solutions 113
2.7 Nonhyperboloidal Balances 114
2.7.1The Single Ring 115
2.7.2 Straubel'sThree Disk Balance 115
2.8 Optical Levitation 117
2.8.1The Optical Levitator. 117
2.8.2The Single-Beam GradientForce Trap 120
2.9AcousticLevitation 123
2.9.1Acoustic Pressure 123
2.9.2The BarotropicFluid 125
2.9.3Energy Density ofan Acoustic Wave 126
2.9.4 Acoustic Pressureon aSphere 127
2.9.5Particle Velocity andPhase Shift.. 130
2.9.6Acoustic Levitators 132
2.9.7Acoustic Measurements 133
2.10References 137
3Elastic Light Scattering 143
3.1Introduction 143
3.2MaxwellEquations 145
3.2.1ConstitutiveRelations 146
3.2.2Time-HarmonicFields 147
3.2.3 Power andEnergy Density 148
3.2.4 Polarization 150
Contents IX
3.3Dipole Radiation 151
3.4Cross SectionsandRadiation Pressure 153
3.4.1 CrossSectionsandEfficiencies 154
3.4.2 Radiation Pressure 155
3.4.3 Radiation Pressure Measurement... 156
3.5Rayleigh Scattering 157
3.5.1 IrradianceofScatteredLight 158
3.5.2PolarizationoftheScatteredLight... 159
3.6ElectromagneticTheory 160
3.6.1MultipoleExpansion 161
3.6.2 Lorenz-MieTheory 162
3.6.3CrossSectionsand Efficiencies 166
3.6.4 Angular Scattering 167
3.6.5Morphology-DependentResonances 169
3.6.6Polarization Ratio 179
3.6.7Electromagnetic Energy Absorption 180
3.6.8Coated Spheres 183
3.7CoupledDipole Theory 185
3.8GeneralizedLorenz-MieTheory 187
3.9The T-matrix Method 190
3.10 Geometrical Optics 192
3.10.1BasicLawsofGeometrical Optics 193
3.10.2 Interfaces 195
3.10.3 Transmitted andScatteredFields 196
3.10.4 Opticsof the Rainbow 201
3.11 Resonances 203
3.11.1 The Localization Principle 204
3.11.2 Resonance Conditions 205
3.11.3 ResonanceCondition forSpherical Geometry 208
3.11.4 Quality factor QandLine Width 210
3.12References 213
4 BasicSingle Particle Measurements 221
4.1 Force Measurement 221
4.2 AerodynamicDrag 223
4.3 LevitationCharacteristics 23I
4.3.1Direct MeasurementofC 231
o
4.3.2 Stability Measurements 233
4.3.3SHEL Data 233
4.3.4 Double-RingMeasurements 234
4.3.5Multiple Particle Trapping 237
4.4 Radiometric andPhoretic Forces 238
4.4.1 Radiation Pressure Force 238
4.4.2 Optical Trap Measurement 239
4.4.3 PhoreticForces 243
X Contents
4.4.4 PhotophoresisMeasurements 243
4.4.5ThennophoresisMeasurements 245
4.5 MassMeasurement. 247
4.6Aerodynamic SizeMeasurement.. 249
4.6.1TheLaminarJet EDB 249
4.6.2Sedimentation 250
4.6.3 Particle StabilityMeasurements 252
4.6.4 PhaseLagMeasurements 254
4.7Optical Size 262
4.7.1 PhaseFunctions 262
4.7.3Polarization Ratio Measurement... 265
4.7.4 Resonance Spectra 266
4.7.5 Diffraction 270
4.7.6 PhaseDopplerAnemometry 276
4.8 Charge Measurement. 287
4.8.1EvaporatingDroplets 287
4.8.2The Rayleigh Limit ofCharge 289
4.8.3Droplet Chain ChargeMeasurement.. 290
4.9 PhotoelectricWork Function 290
4.10References 295
5ContinuumTransport Processes .301
5.1Transport Regimes 301
5.2ThermalEnergyEquation 303
5.3ConvectiveDiffusion Equation .305
5.4 EquationsofMotion 306
5.4.1 StokesFlow 307
5.4.2HigherOrder Solutions .308
5.4.3 Fluid Spheres .309
5.4.4Ellipsoidal Particles 310
5.4.5 Other Non-spherical Particles 314
5.5HeatTransfer .317
5.5.1 StagnantFluid 317
5.5.2Electromagnetic Heating .320
5.5.3Internal Temperatureswith Pulsed Heating 321
5.5.4 External TemperaturesinPulsed Heating 330
5.5.5Particle Cooling byThermal Emission 332
5.6MassTransfer 333
5.6.1 HeatandMassFlux Relations 334
5.6.2 Single Component Droplet Evaporation 336
5.6.3 Quasi-SteadyState 345
5.6.4 MulticomponentEvaporation Measurements .357
5.6.5Condensational Particle Growth 361
5.7ConvectiveTransportProcesses 363
5.7.1 HeatandMassTransfer withStokesFlow 363