Laser chemistry: spectroscopy, dynamics and applications

517 Pages·2007·8.93 MB·English

by  Helmut H. Telle, Angel González Ureña, Robert J. Donovan

Laser Chemistry

Laser Chemistry
Spectroscopy, Dynamics and Applications
Helmut H. Telle Swansea University, UK
Angel Gonza´lez Uren˜a Universidad Complutense de Madrid, Spain
Robert J. Donovan Edinburgh University, UK
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Telle,HelmetH.
Laserchemistry:spectroscopy,dynamicsandapplications/HelmetH.Telle,AngelGonzalezUrena,RobertJ.Donovan.
p.cm.
Includesbibliographicalreferencesandindex.
ISBN978-0-471-48570-4(cloth:alk.paper)
1. Lasersinchemistry. I.Urena,AngelGonzalez.II.Donovan,Robert
J.(RobertJohn),1941-III.Title.
QD701.T452007
542–dc22 2007010277
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ISBN978-0-471-48570-4(HB)ISBN100-471-48570-5(HB)
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Contents
Preface xi
About the authors xiii
1 Introduction 1
1.1 Basicconcepts inlaserchemistry 1
1.2 Organizationofthebook 10
PART 1 PRINCIPLES OF LASERS AND LASER SYSTEMS 15
2 Atoms and molecules, and their interaction with light waves 17
2.1 Quantumstates,energylevels andwavefunctions 17
2.2 Dipoletransitionsandtransitionprobabilities 20
2.3 Einsteincoefficientsandexcited-statelifetimes 23
2.4 Spectroscopiclineshapes 24
2.5 Thepolarizationoflightwaves 26
2.6 Basicconcepts ofcoherence 26
2.7 Coherentsuperposition ofquantumstates andtheconcept ofwavepackets 29
3 The basics of lasers 35
3.1 Fundamentalsoflaseraction 35
3.2 Laserresonators 39
3.3 Frequencyandspatialproperties oflaserradiation 41
3.4 Gainincontinuous-waveandpulsedlasers 43
3.5 Q-switchingandthegeneration ofnanosecondpulses 45
3.6 Modelockingandthegeneration ofpicosecondandfemtosecond pulses 48
4 Laser systems 51
4.1 Fixed-wavelengthgaslasers:helium–neon,rare-gasionandexcimerlasers 51
4.2 Fixed-wavelengthsolid-statelasers: theNd:YAGlaser 55
4.3 Tuneable dyelasersystems 57
4.4 Tuneable Ti:sapphirelasersystems 60
4.5 Semiconductordiodelasers 63
4.6 Quantumcascadelasers 67
4.7 Non-linearcrystalsandfrequency-mixingprocesses 68
4.8 Three-wavemixingprocesses: doubling,sumand
differencefrequency 72
4.9 Opticalparametricoscillation 74
vi CONTENTS
PART 2 SPECTROSCOPIC TECHNIQUES IN LASER CHEMISTRY 77
5 General concepts of laser spectroscopy 79
5.1 Spectroscopybasedonphotondetection 80
5.2 Spectroscopybasedoncharged particledetection 81
5.3 Spectroscopybasedonmeasuringchangesofmacroscopicphysicalproperties
ofthemedium 82
6 Absorption spectroscopy 87
6.1 Principlesofabsorptionspectroscopy 87
6.2 Observabletransitionsinatomsandmolecules 89
6.3 Practicalimplementationofabsorptionspectroscopy 91
6.4 Multipassabsorptiontechniques 95
7 Laser-induced fluorescence spectroscopy 101
7.1 Principlesoflaser-inducedfluorescencespectroscopy 102
7.2 Importantparameters inlaser-inducedfluorescence 105
7.3 Practicalimplementationoflaser-inducedfluorescencespectroscopy 113
8 Light scattering methods: Raman spectroscopy and other processes 119
8.1 Lightscattering 119
8.2 PrinciplesofRamanspectroscopy 121
8.3 PracticalimplementationofRamanspectroscopy 125
9 Ionization spectroscopy 129
9.1 Principlesofionizationspectroscopy 129
9.2 Photoiondetection 131
9.3 Photoelectrondetection 135
9.4 Photoionimaging 138
PART 3 OPTICS AND MEASUREMENT CONCEPTS 143
10 Reflection, refraction and diffraction 145
10.1 Selected propertiesofopticalmaterials andlightwaves 145
10.2 Reflectionandrefractionataplanesurface 149
10.3 Lighttransmissionthroughprisms 153
10.4 Lighttransmissionthroughlensesandimaging 155
10.5 Imagingusingcurvedmirrors 158
10.6 Superposition,interference anddiffractionoflightwaves 158
10.7 Diffraction bysingleandmultipleapertures 161
10.8 Diffraction gratings 164
11 Filters and thin-film coatings 169
11.1 Attenuation oflightbeams 169
11.2 Beamsplitters 170
11.3 Wavelength-selectivefilters 172
11.4 Polarization filters 173
11.5 Reflectionand filteringatopticalcomponent interfaces 176
11.6 Thin-filmcoatings 177
CONTENTS vii
12 Optical fibres 183
12.1 Principlesofopticalfibretransmission 183
12.2 Attenuationinfibretransmission 185
12.3 Modepropagationinfibres 186
13 Analysis instrumentation and detectors 189
13.1 Spectrometers 189
13.2 Interferometers 190
13.3 Photondetectorsexploitingthephotoelectric effect 193
13.4 Photodetectorsbasedonband-gapmaterials 194
13.5 Measuringlaserpowerandpulseenergy 197
13.6 Analysisofchargedparticles forcharge,massand energy 198
13.7 Charged-particle detectors 202
14 Signal processing and data acquisition 205
14.1 Signals,noiseandnoisereduction 205
14.2 DC,ACandbalanceddetectionmethods 208
14.3 Lock-indetection techniques 209
14.4 Gatedintegration/boxcar averaging techniques 212
14.5 Eventcounting 213
14.6 Digitalconversionanddata acquisition 216
PART 4 LASER STUDIES OF PHOTODISSOCIATION,
PHOTOIONIZATION AND UNIMOLECULAR PROCESSES 219
15 Photodissociation of diatomic molecules 223
15.1 Photofragmentkineticenergy 223
15.2 Angulardistributions andanisotropicscattering 225
15.3 Predissociationand curvecrossing 226
15.4 Femtosecondstudies:chemistryinthefastlane 228
15.5 Dissociationandoscillatory continuumemission 230
16 Photodissociation of triatomic molecules 233
16.1 Photodissociationofwater 233
16.2 Photodissociationofozone 235
16.3 Laser-induced fluorescenceandcavityring-downstudies 238
16.4 Femtosecondstudies:transition-statespectroscopy 238
17 Photodissociation of larger polyatomic molecules:
energy landscapes 241
17.1 Rydbergtagging 241
17.2 Photodissociationofammonia 242
17.3 Selectivebondbreaking 243
17.4 Moleculareliminationandthree-bodydissociation 244
18 Multiple and multiphoton excitation,
and photoionization 245
18.1 Infraredmultiple-photon activationandunimoleculardissociation 246
18.2 Continuumintermediate states andbondstretching 247
viii CONTENTS
18.3 High-resolutionzerokineticenergyphotoelectron spectroscopy 251
18.4 Autoionization 254
18.5 Photoion-pairformation 256
19 Coherent control and the future of ultra-short probing 259
19.1 Coherent controlofchemicalprocesses 259
19.2 Time-resolveddiffraction andattosecondprobing 263
PART 5 LASER STUDIES OF BIMOLECULAR REACTIONS 265
20 Basic concepts of kinetics and reaction dynamics 267
20.1 Re´sume´ ofkinetics 267
20.2 Introductiontoreactiondynamics: totaland differential reactioncross-sections 269
20.3 TheConnection betweendynamicsandkinetics 272
20.4 Basic conceptsofpotentialenergysurfaces 273
20.5 Calculatingpotentialenergysurfaces 276
21 The molecular beam method: basic concepts and examples
of bimolecular reaction studies 279
21.1 Basicconcepts 279
21.2 Interpretationofspatialandenergydistributions:dynamicsofatwo-bodycollision 283
21.3 Interpretationofspatialandenergydistributions:productangularand velocitydistributions
asaroutetothereactionmechanism 289
22 Chemical reactions with laser-prepared reagents 295
22.1 Energyselectivity:mode-selectivechemistry 295
22.2 Energyselectivity:electronicexcitation 296
22.3 Stereodynamical effectswithlaser-prepared reagents 300
23 Laser probing of chemical reaction products 307
23.1 Wheredoes theenergyofachemicalreaction go? 307
23.2 Probingtheproductstatedistributionofachemicalreaction 307
23.3 Crossed-beamtechniquesandlaserspectroscopicdetection:towards thestate-to-state
differentialreaction cross-sectionmeasurements 309
PART 6 LASER STUDIES OF CLUSTER AND
SURFACE REACTIONS 323
24 Laser studies of complexes: Van der Waals and
cluster reactions 327
24.1. Experimental set-upsandmethodologies 327
24.2. Metal-containing complexes 332
24.3. Non-metalvanderWaalscomplexes 339
25 Solvation dynamics: elementary reactions in solvent cages 349
25.1. Dissociationofclusters containingI 349
2
25.2. Dissociationofclusters containingI(cid:1) 350
2
25.3. Proton-transferreactions 353
CONTENTS ix
26 Laser studies of surface reactions: an introduction 357
26.1. Re´sume´ ofmetal surfacepropertiesandelectronic structure 357
26.2. Particle–surfaceinteraction 360
26.3. Surfacereaction mechanisms 364
26.4. Experimentalmethods toinvestigatelaser-inducedsurfacereactions 367
27 Laser studies of surface reactions: photochemistry in the adsorbed state 371
27.1. Adsorbate-versussubstrate-mediated processes 371
27.2. Examplesofphotoinducedreactionsinadsorbates 378
27.3. Femto-chemistryatsurfaces: theultrafast reactionCO/O—[Ru(0001)] 387
PART 7 SELECTED APPLICATIONS 391
28 Environmental and other analytical applications 393
28.1 Atmosphericgas monitoringusingtuneablediodelaserabsorptionspectroscopy 394
28.2 Closed-pathtuneablediodelaserabsorptionspectroscopyapplications 398
28.3 Open-pathtuneablediodelaserabsorptionspectroscopyapplications 403
28.4 Thelidartechniqueforremoteanalysis 409
28.5 Lidarinthestudyofatmosphericchemistry: troposphericmeasurements 412
28.6 Lidarinthestudyofatmosphericchemistry: stratosphericmeasurements 419
28.7 Laserdesorptionandionization: laser-inducedbreakdownspectroscopy,matrix-assisted
laserdesorptionandionization,andaerosoltime-of-flight massspectrometry 422
29 Industrial monitoring and process control 433
29.1 Laser-spectroscopic analysisofinternalcombustionengines 433
29.2 Laser-spectroscopic analysisofburnersandincinerators 438
29.3 Laser-chemical processes atsurfaces: nanoscalepatterning 444
30 Laser applications in medicine and biology 449
30.1 Photodynamictherapy 449
30.2 Intra-cellmappingofdrugdeliveryusingRamanimaging 453
30.3 Breathdiagnostics usinglaserspectroscopy 455
30.4 Fromphotonstoplantdefence mechanisms 460
30.5 Applicationtovolatilecompounds:on-linedetectionofplantstress 461
30.6 Laserapplications tothestudyofnon-volatilecompoundsinfruits 463
References 471
Referencesgroupedbychapter 471
Furtherreadinggroupedbypart 482
Webpages 483
Appendix 485
Commonabbreviationsandacronyms 485
Physicalconstants 486
Usefulconversionsandother relationships 486
Energyconversionfactors 486
Index 487