Fundamentals and Applications in Aerosol Spectroscopy

Fundamentals and

Applications in

Aerosol Spectroscopy

Fundamentals and

Applications in

Aerosol Spectroscopy

Edited by

Ruth Signorell ■ Jonathan P. Reid

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v

Contents

Preface...............................................................................................................................................ix

Editors............................................................................................................................................ xiii

Contributors.....................................................................................................................................xv

ion ISect Infrared Spectroscopy

1Chapter Infrared Spectroscopy of Aerosol Particles .................................................................3

Thomas Leisner and Robert Wagner

2Chapter Vibrational Excitons: A Molecular Model to Analyze Infrared

Spectra of Aerosols .............................................................................................. 25

George Firanescu, Thomas C. Preston, Chia C. Wang, and Ruth Signorell

3Chapter Aerosol Nanocrystals of Water Ice: Structure, Proton Activity, Adsorbate

Effects, and H-Bond Chemistry.................................................................................49

J. Paul Devlin

4Chapter Infrared Extinction and Size Distribution Measurements

of Mineral Dust Aerosol ......................................................................................79

Paula K. Hudson, Mark A. Young, Paul D. Kleiber, and Vicki H. Grassian

5Chapter Infrared Spectroscopy of Dust Particles in Aerosols for Astronomical

Application ....................................................................................................... 101

Akemi Tamanai and Harald Mutschke

ion IISect Raman Spectroscopy

6Chapter Linear and Nonlinear Raman Spectroscopy of Single Aerosol Particles................ 127

N.-O. A. Kwamena and Jonathan P. Reid

7Chapter Raman Spectroscopy of Single Particles Levitated by an Electrodynamic

Balance for Atmospheric Studies............................................................................. 155

Alex K. Y. Lee and Chak K. Chan

vi Contents

Chapter 8 Micro-Raman Spectroscopy for the Analysis of Environmental Particles.............. 193

Sanja Potgieter-Vermaak, Anna Worobiec, Larysa Darchuk,

and Rene Van Grieken

Chapter 9 Raman Lidar for the Characterization of Atmospheric Particulate Pollution .........209

Detlef Müller

Section III VIS/UV Spectroscopy, Fluorescence,

and Scattering

Chapter 10 UV and Visible Light Scattering and Absorption Measurements on

Aerosols in the Laboratory.......................................................................................243

Zbigniew Ulanowski and Martin Schnaiter

Chapter 11 Progress in the Investigation of Aerosols’ Optical Properties Using

Cavity Ring-Down Spectroscopy: Theory and Methodology..................................269

Ali Abo Riziq and Yinon Rudich

Chapter 12 Laser-Induced Fluorescence Spectra and Angular Elastic Scattering Patterns

of Single Atmospheric Aerosol Particles .................................................................297

R. G. Pinnick, Y. L. Pan, S. C. Hill, K. B. Aptowicz, and R. K. Chang

Chapter 13 Femtosecond Spectroscopy and Detection of Bioaerosols....................................... 321

Luigi Bonacina and Jean-Pierre Wolf

Chapter 14 Light Scattering by Fractal Aggregates ................................................................... 341

C. M. Sorensen

Section IV UV, X-ray, and Electron Beam Studies

Chapter 15 Aerosol Photoemission............................................................................................. 367

Kevin R. Wilson, Hendrik Bluhm, and Musahid Ahmed

Chapter 16 Elastic Scattering of Soft X-rays from Free Size-Selected Nanoparticles............... 401

Harald Bresch, Bernhard Wassermann, Burkhard Langer, Christina Graf, and

Eckart Rühl

Contents vii

Chapter 17 Scanning Transmission X-ray Microscopy: Applications in

Atmospheric Aerosol Research................................................................................ 419

Ryan C. Moffet, Alexei V. Tivanski, and Mary K. Gilles

Chapter 18 Electron Beam Analysis and Microscopy of Individual Particles...........................463

Alexander Laskin

Index.............................................................................................................................................. 493

ix

Preface

This book is intended to provide an introduction to aerosol spectroscopy and an overview of the

state-of-the-art of this rapidly developing field. It includes fundamental aspects of aerosol spectro￾scopy as well as applications to atmospherically and astronomically relevant problems. Basic knowl￾edge is the prerequisite for any application. However, in aerosol spectroscopy, as in many other

fields, there remain crucial gaps in our understanding of the fundamental processes. Filling this gap

can only be a first step, with the challenge then remaining to develop instruments and methods

based on those fundamental insights, instruments that can easily be used to study aerosols in plan￾etary atmospheres as well as in space. With this in mind, this book also touches upon some of the

aspects that need further research and development. As a guideline, the chapters in this book are

arranged in the order of decreasing wavelength of light/electrons, starting with infrared spectros￾copy and concluding with x-ray and electron beam studies.

Infrared spectroscopy is one of the most important aerosol characterization methods in labora￾tory studies, for field measurements, for remote sensing, and in space missions. It provides a wealth

of information about aerosol particles ranging from properties such as particle size and shape to

information on their composition and chemical reactivity. The analysis of spectral information,

however, is still a challenge. In Chapter 1, Leisner and Wagner provide a detailed description of the

most widely used method to analyze infrared extinction spectra, namely classical scattering theory

in combination with continuum models of the optical properties of aerosol particles. The authors

explain how information such as number concentration, size distribution, chemical composition,

and shape can be retrieved from infrared spectra, and outline where pitfalls could occur. Theoretical

considerations are illustrated with experiments performed in the large cloud chamber, aerosol inter￾action and dynamics in the atmosphere (AIDA).

Classical scattering theory and continuum models for optical properties are not always suitable

for a detailed analysis of particle properties. Available optical data are often not accurate enough,

and for small particles, where the molecular structure becomes important, these methods fail alto￾gether. In Chapter 2, Firanescu, Preston, Wang, and Signorell discuss a molecular model that allows

a detailed analysis of particle properties on the basis of the band shapes observed in infrared extinc￾tion spectra. In particular, this approach explains why and when infrared spectra of molecular

aerosols are determined by particle properties such as shape, size, or architecture. After a descrip￾tion of the approach, the authors illustrate its application by means of a variety of examples.

Water and ice are the most important components of aerosols in our Earth’s atmosphere. They

play a crucial role in many atmospheric processes. Water ice is also ubiquitous beyond our planet

and solar system. In Chapter 3, Devlin uses infrared spectroscopy to characterize this important

type of particle and shows how the structural properties of pure and mixed ice nanocrystals can be

unraveled by this technique. Special consideration is given to the nature of the surface of these

particles, the role it plays, and how it is influenced by adsorbates. The formation and transformation

of numerous naturally occurring hydrates are discussed. These studies reveal the exceptional prop￾erties of water ice surfaces.

Chapters 4 and 5 are devoted to the infrared spectroscopy of dust particles. The infrared radia￾tive effects of mineral dust aerosols in the Earth’s atmosphere are investigated by Hudson, Young,

Kleiber, and Grassian in Chapter 4. Remote sensing studies using infrared data from satellites pro￾vide the source of information to determine the radiative effects of these particles. Such data are

commonly analyzed using Mie theory, which treats all particles as spheres. The authors discuss

the errors associated with this assumption and demonstrate that the proper treatment of particle

x Preface

shape is crucial in retrieving reliable information about the radiative effect of mineral dust particles

from remote sensing. The properties of dust grains occurring in astrophysical environments are the

subject of Chapter 5 by Tamanai and Mutschke. Dust grains of different composition with sizes in

the micrometer range are widely distributed throughout space. Ground-based as well as satellite￾based telescopes are used for infrared studies of these dust particles. Tamanai and Mutschke dis￾cuss infrared laboratory studies of astrophysically relevant dust grains and their application to the

interpretation of astronomical spectra. While the wide variety of dust properties makes spectral

analysis a difficult task, the authors demonstrate that important information can be obtained from

such measurements about the conditions under which dust grains exist and evolve in astronomical

environments.

Raman spectroscopy has proved to be a versatile tool for examining aerosol particles in con￾trolled laboratory measurements, allowing the unambiguous identification of chemical species, the

determination of particle composition, and even the determination of particle size and temperature.

Although Raman scattering is inherently a weak process, measurements have been routinely per￾formed on droplet trains using pulsed laser and continuous-wave laser techniques, on aerosol parti￾cles isolated in optical or electrodynamic traps, and on particles deposited on substrates. Section II

begins with a general introduction to the fundamentals of both linear and nonlinear Raman scatter￾ing from aerosol particles. In particular, Kwamena and Reid highlight the considerable accuracy

(<1 nm) that can be achieved in the determination of droplet size from the unique fingerprint of

enhanced Raman scattering that occurs at discrete wavelengths commensurate with whispering gal￾lery modes, also referred to as morphology-dependent resonances. Before reviewing some recent

applications of Raman spectroscopy for characterizing aerosol, they introduce some of the key

experimental considerations that must be remembered when designing a Raman instrument for

aerosol studies. Lee and Chan describe the coupling of Raman spectroscopy with an electrody￾namic balance in Chapter 7, outlining how information gained from Raman measurements can

complement that from other methods, including light scattering for probing particle size and mor￾phology, or tracking evolving particle mass. In particular, they review recent studies of hygroscopic￾ity and heterogeneous chemistry. They demonstrate that resolving Raman line shapes can provide

important insights into intermolecular interactions between solvent and solute molecules within the

condensed aerosol phase, particularly important for understanding the properties of metastable

supersaturated states accessed at high solute concentrations.

Raman analysis can provide an important tool for characterizing particulate matter of atmo￾spheric origin as well as for probing particles in controlled laboratory measurements. Potgieter￾Vermaak, Worobiec, Darchuk, and Van Grieken review the application of micro-Raman spectroscopy

for the analysis of environmental particles in Chapter 8. They begin by reviewing the methods avail￾able for ambient sampling and the importance of choosing suitable substrates, before discussing the

advantages and challenges of utilizing the technique on a stand-alone basis. The practicalities of

coupling micro-Raman measurements with other techniques, such as scanning electron microscopy

coupled with energy-dispersive x-ray spectrometric detection, are also described and assessed.

Key uncertainties remain in the direct and indirect impact of aerosols on climate, and coordi￾nated monitoring of the temporal variability of global aerosol distribution is a basic requirement

of climate research. In Chapter 9, Müller describes the application of Raman LIDAR (light detec￾tion and ranging) in the characterization of atmospheric pollution. After a description of the basic

principles of Raman LIDAR, methods for deriving the optical and microphysical properties of

particulate pollution are introduced. This is followed by an illustration of the potential of modern

Raman LIDARs, particularly when measurements are made with a network of systems on a con￾tinental scale.

Elastic light scattering by particles in the visible and UV parts of the electromagnetic spectrum

provides the basis for many conventional and routine techniques for determining particle size and

concentration. More recently, it has been shown that resolving the light scattering from single

particles may lead to the development of new instruments for assessing particle size and shape.

Preface xi

In addition, fluorescence spectroscopy is becoming an increasingly applied technique for identify￾ing particle composition. Ulanowski and Schnaiter begin Section III with a discussion of light scat￾tering and absorption measurements on aerosols in the laboratory. Following an introduction to key

parameters that must be typically measured, they review some of the common methods for perform￾ing extinction spectroscopy, using an optical extinction cell, and absorption spectroscopy, specifi￾cally photoacoustic spectroscopy, and applications of these instruments in laboratory and chamber

measurements. Resolving the angular dependence of light scattering has a long history in the field

of particle analysis, and recent developments have concentrated on the measurement and analysis of

complex morphologies recorded at the single-particle level, allowing the categorization of sampled

particles into distinct classes.

In Chapter 11, Riziq and Rudich describe the information that can be gained by measuring light

extinction from ensembles of accumulation mode aerosol particles using cavity ring-down spectros￾copy (CRD-S). CRD-S is widely used for performing highly sensitive measurements of gas-phase

composition and is now becoming more extensively used in both field and laboratory-based aerosol

measurements. The authors introduce the underlying principles of CRD-S, before describing pulsed

and continuous-wave implementations of the technique, and the sensitivity that can be achieved.

The chapter concludes with a review of recent applications, particularly focusing on the retrieval of

aerosol optical properties.

The application of laser-induced fluorescence (LIF) spectroscopy for identifying and classifying

biological aerosol particles is described by Pinnick, Pan, Hill, Aptowicz, and Chang in Chapter 12.

Although many compounds have similar fluorescence spectra with relatively broad and indistin￾guishable features, unlike those that occur in Raman or IR spectra, single-particle LIF measure￾ments can provide clear and distinguishable signatures for different classes of biological and

anthropogenic aerosol. Further classification of particle type/morphology can be achieved by two￾dimensional angular optical scattering (TAOS), complementing and expanding on the discussion of

this technique provided by Ulanowski and Schnaiter in Chapter 10. Bonacina and Wolf describe the

improved specificity of bioaerosol detection that can be achieved using ultrafast laser techniques,

including time-resolved pump–probe fluorescence spectroscopy, femtosecond laser-induced break

down spectroscopy, and coherent optimal control in Chapter 13. In particular, they show that the

application of an ultrafast double-pulse excitation scheme can induce strong fluorescence depletion

from biological samples such as bacteria-containing droplets, allowing discrimination from possi￾ble interferents, such as polycyclic aromatic compounds, which otherwise have similar spectro￾scopic properties.

In many optical studies of aerosols, particles can be assumed to be spherical in shape, allowing

the application of Mie scattering theory. In many cases, this only provides an approximate picture

and the application of more rigorous treatments that describe the nonspherical morphology of a

particle must be considered. Sorensen explores the complexity apparent in scattering measurements

from fractal aggregates in Chapter 14, concentrating on diffusion-limited cluster aggregates. The

theoretical treatment of such particles is based on the Rayleigh–Debye–Gans (RDG) approxima￾tion, which assumes that the monomeric units forming the aggregate scatter light independently.

Once the fundamental concepts describing scattering in such complex systems have been intro￾duced, the absolute scattering and differential cross-sections are defined, and the methods used in

the analysis of data recorded from polydisperse systems are described.

Section IV deals with VUV, x-ray, and electron beam studies of aerosols. All these techniques

constitute fairly new ways of characterizing aerosols, many aspects of which have been developed

in recent years by the authors of these chapters. This book contains a unique overview of the differ￾ent aspects and prospects of these methods. Photoelectron spectroscopy as applied to aerosol sci￾ence is the subject of Chapter 15 by Wilson, Bluhm, and Ahmed, who provide a comprehensive

overview of the techniques, the history, and the literature in the field. The use of photoelectric

charging to probe surface composition and chemical as well as physical properties of aerosols is

demonstrated by various examples in the second part of their chapter. The third part demonstrates,

xii Preface

with many examples, how synchrotron-based aerosol photoemission can be used to unravel chemi￾cal information on the interfaces and properties of biological nanoparticles. Bresch, Wassermann,

Langer, Graf, and Rühl demonstrate in Chapter 16 how x-ray light scattering allows them to obtain

information on aerosol properties such as surface properties or size. The use of tunable x-rays for

the aerosol scattering experiment is an exciting new approach. The authors present novel experi￾mental results and developments for the proper analysis of the observed scattering patterns.

New approaches to characterize aerosols by scanning x-ray transmission microscopy and elec￾tron microscopy are presented in Chapter 17 by Moffet, Tivanski, and Gilles and in Chapter 18 by

Laskin. Chapter 17 provides a unique introduction to scanning transmission x-ray microscopy and

the latest developments in this field. This is the first and so far only comprehensive overview of this

promising technique to become available in the literature. The power of this technique for the char￾acterization of atmospherically relevant aerosols is illustrated by applying the method to aerosol

samples collected from various sources in different field campaigns. The authors outline how infor￾mation on aerosol morphology, surface coating, mixing state, and atmospheric processing can be

extracted from such measurements. Following this overview of scanning x-ray transmission micros￾copy, Laskin gives a similarly unique review of electron beam microscopy studies of aerosols and

complementary microspectroscopic methods in Chapter 18. Besides many other particle properties,

the microanalysis of aerosol particles allows one to retrieve information on the lateral distribution

of chemical species within individual particles. In one of his examples, the author shows how chem￾ical information is extracted from studies of field-collected particles. In another, he reports on the

use of electron microscopy to study the hygroscopic properties and ice nucleation of individual

particles.

Our special thanks go to all authors who have contributed their time and expertise to this over￾view of the spectroscopy of aerosols. We hope that the result is as enjoyable as it is informative, not

only for aerosol scientists but also for students and other readers interested in the field.

MATLAB® is a registered trademark of The MathWorks, Inc. For product information, please

contact:

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Ruth Signorell

Jonathan P. Reid

xiii

Editors

Ruth Signorell received undergraduate and postgraduate degrees from ETH Zürich in Switzerland

before moving to a postdoctoral fellowship at the University of Göttingen in Germany where she

became assistant professor in 2002. Since 2005, she has been professor in physical and analytical

chemistry at the University of British Columbia in Canada. She has been awarded the ETH Medal

in 1999 for her PhD thesis, the 2005 Werner Award of the Swiss Chemical Society, an A. P. Sloan

Fellowship from the United States in 2007, the 2009 Thermo Fisher Scientific Spectroscopy Award

from the Canadian Society for Analytical Sciences and Spectroscopy, and the 2010 Keith Laidler

Award from the Canadian Society for Chemistry. Her research interests focus on infrared and

extreme ultraviolet studies of aerosols.

Jonathan P. Reid received undergraduate and postgraduate degrees from the University of Oxford

(MA, DPhil) before moving to a postdoctoral fellowship at JILA, University of Colorado. In 2000,

he took up a lectureship at the University of Birmingham, United Kingdom, before moving to the

University of Bristol, United Kingdom, in 2004. He is currently professor in physical chemistry and

a Leadership Fellow of the Engineering and Physical Sciences Research Council. He was awarded

the 2001 Harrison Memorial Prize and the 2004 Marlow Medal by the Royal Society of Chemistry.

His research interests focus on developing new techniques to characterize and manipulate aerosol

particles using light.

xv

Contributors

Musahid Ahmed

Chemical Sciences Division

Lawrence Berkeley National Laboratory

Berkeley, California

K. B. Aptowicz

Department of Physics

West Chester University

West Chester, Pennsylvania

Hendrik Bluhm

Chemical Sciences Division

Lawrence Berkeley National Laboratory

Berkeley, California

Luigi Bonacina

University of Geneva—GAP-Biophotonics

Rue de l’Ecole de Medecine

Geneva, Switzerland

Harald Bresch

Physikalische Chemie

Freie Universität Berlin

Berlin, Germany

Chak K. Chan

Division of Environment

Hong Kong University of Science and

Technology

Kowloon, Hong Kong, China

R. K. Chang

Department of Applied Physics

Yale University

New Haven, Connecticut

Larysa Darchuk

Department of Chemistry

University of Antwerp (Campus Drie Eiken)

Universiteitsplein, Wilrijk-Antwerpen, Belgium

J. Paul Devlin

Department of Chemistry

Oklahoma State University

Stillwater, Oklahoma

George Firanescu

Department of Chemistry

University of British Columbia

Vancouver, British Columbia, Canada

Mary K. Gilles

Chemical Sciences Division

Lawrence Berkeley National Laboratory

Berkeley, California

Christina Graf

Physikalische Chemie

Freie Universität Berlin

Berlin, Germany

Vicki H. Grassian

Department of Physics and Astronomy

University of Iowa

Iowa City, Iowa

S. C. Hill

U.S. Army Research Laboratory

Adelphi, Maryland

Paula K. Hudson

Center for Global and Regional Environmental

Research

University of Iowa

Iowa City, Iowa

Paul D. Kleiber

Department of Physics and Astronomy

University of Iowa

Iowa City, Iowa

Nana Kwamena

School of Chemistry

University of Bristol

Bristol, United Kingdom

Burkhard Langer

Physikalische Chemie

Freie Universität Berlin

Berlin, Germany

xvi Contributors

Alexander Laskin

W. R. Wiley Environmental Molecular Science

Laboratory

Pacific Northwest National Laboratory

Richland, Washington

Alex K. Y. Lee

Department of Chemical and Biomolecular

Engineering

Hong Kong University of Science and

Technology

Kowloon, Hong Kong, China

Thomas Leisner

Karlsruhe Institute of Technology

Institute for Meteorology and Climate

Research

Hermann-von-Helmholtz-Platz

Eggenstein-Leopoldshafen, Germany

Ryan C. Moffet

Chemical Sciences Division

Lawrence Berkeley National Laboratory

Berkeley, California

Detlef Müller

Atmospheric Remote Sensing Laboratory

Gwangju Institute of Science and

Technology

Gwangju, Republic of Korea

and

Department of Physics

Leibniz Institute for Tropospheric

Research

Leipzig, Germany

Harald Mutschke

Astrophysical Institute and University

Observatory

Friedrich-Schiller-University Jena

Schillergäßchen, Jena, Germany

Y. L. Pan

U.S. Army Research Laboratory

Adelphi, Maryland

R. G. Pinnick

U.S. Army Research Laboratory

Adelphi, Maryland

Sanja Potgieter-Vermaak

Department of Chemistry

University of Antwerp

(Campus Drie Eiken),

Universiteitsplein, Wilrijk-Antwerpen,

Belgium

Thomas C. Preston

Department of Chemistry

University of British Columbia

Vancouver, British Columbia, Canada

Jonathan P. Reid

School of Chemistry

University of Bristol

Bristol, United Kingdom

Ali Abo Riziq

Department of Environmental Sciences

Weizmann Institute

Rehovot, Israel

Yinon Rudich

Department of Environmental

Sciences

Weizmann Institute

Rehovot, Israel

Eckart Rühl

Physikalische Chemie

Freie Universität Berlin

Berlin, Germany

Martin Schnaiter

Karlsruhe Institute of Technology

Institute for Meteorology and Climate

Research

Hermann-von-Helmholtz-Platz

Eggenstein-Leopoldshafen,

Germany

C. M. Sorensen

Department of Physics

Kansas State University

Manhattan, Kansas

Akemi Tamanai

Astrophysical Institute and University

Observatory

Friedrich-Schiller-University Jena

Schillergäßchen, Jena, Germany

Contributors xvii

Alexei V. Tivanski

Chemical Sciences Division

Lawrence Berkeley National Laboratory

Berkeley, California

Zbigniew Ulanowski

Centre for Atmospheric and Instrumentation

Research

University of Hertfordshire, Hatfield

Herts, United Kingdom

Rene Van Grieken

Department of Chemistry

University of Antwerp (Campus Drie Eiken)

Universiteitsplein, Wilrijk-Antwerpen,

Belgium

Robert Wagner

Karlsruhe Institute of Technology

Institute for Meteorology and Climate Research

Hermann-von-Helmholtz-Platz

Eggenstein-Leopoldshafen, Germany

Chia C. Wang

Department of Chemistry

University of British Columbia

Vancouver, British Columbia, Canada

Bernhard Wassermann

Physikalische Chemie

Freie Universität Berlin

Berlin, Germany

Kevin R. Wilson

Chemical Sciences Division

Lawrence Berkeley National Laboratory

Berkeley, California

Jean-Pierre Wolf

University of Geneva—GAP￾Biophotonics

Rue de l’Ecole de Medecine

Geneva, Switzerland

Anna Worobiec

Department of Chemistry

University of Antwerp

(Campus Drie Eiken)

Universiteitsplein, Wilrijk-Antwerpen,

Belgium

Mark A. Young

Department of Chemistry

University of Iowa

Iowa City, Iowa