Modern Techniques in Raman Spectroscopy Edited by J.J. Laserna University of Malaga, Spain

JOHN WILEY & SONS Chichester • New York • Brisbane • Toronto • Singapore

CONTENTS

LIST OF CONTRIBUTORS PREFACE

xv xvii

Chapter 1 SIGNAL EXPRESSIONS IN RAMAN SPECTROSCOPY C.L. Stevenson and T. Vo-Dinh 1 INTRODUCTION 2 THEORY: RAMAN SCATTERING INTENSITY 2.1 Classical Theory of Light Scattering from Molecules 2.1.1 Scatter from isotropic molecules 2.1.2 Scatter from anisotropic molecules 2.1.3 Raman scatter 2.2 Quantum-Mechanical Theory of Light Scattering from Molecules 2.3 Selection Rules for Raman Scatter 2.4 Enhanced Raman Scattering 2.4.1 Introduction: Raman scattering efficiency 2.4.2 Resonance Raman scattering 2.4.3 Surface-enhanced Raman scattering (SERS) 3 MEASUREMENTS OF RAMAN SCATTER 3.1 The Measurement Process 3.2 Signal Collection and Detection 3.3 Signal-to-Noise Ratio of Raman Measurements 3.4 Sources of Noise in Raman Measurements 4 RAMAN INSTRUMENTATION: EFFECT ON S/N 5 CONCLUSIONS. 6 ACKNOWLEDGMENTS 7 REFERENCES

1 2 2 3 7 12 16 19 21 21 22 23 26 26 27 30 33 35 37 37 38

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Contents

Chapter 2

INSTRUMENTATION FOR DISPERSIVE RAMAN SPECTROSCOPY R.L. McCreery

1 INTRODUCTION 2 RAMAN DETECTION PRINCIPLES 2.1 The Raman Detection Problem 2.2 Signal to Noise Ratio Expressions 2.3 General Design Considerations 2.3.1 Choice of laser wavelength 2.3.2 Detector area 2.3.3 Resolution/spectral coverage trade-off 3 CHARACTERISTICS OF INSTRUMENT COMPONENTS 3.1. Lasers 3.2 Sampling Modes and Collection Optics 3.2.1 The 90° collection geometry 3.2.2 The 180° geometry 3.2.3 Fiber optic sampling 3.3 Spectrographs and Filters 3.3.1 Double monochromators 3.3.2 Triple monochromators 3.3.3 Single spectrographs 3.4 Detectors 4 CALIBRATION 4.1 Frequency Calibration 4.1.1 Wavelength Standards 4.1.2 Raman shift Standards 4.2 Intensity Calibration 5 FT RAMAN COMPARED WITH DISPERSIVE RAMAN 6 SUPPLIERS 7 REFERENCES Chapter 3

41 42 42 45 47 47 47 47 48 48 51 52 53 54 56 56 57 58 59 61 61 62 62 65 66 70 72

FOURIER TRANSFORM RAMAN SPECTROSCOPY P.J. Hendra

1 INTRODUCTION 2 EXPERIMENTAL ARRANGEMENTS 2.1 Sampling Systems 2.2 Operational Conditions 2.3 Data Processing and Library Searching 2.4 Quantitative Raman Studies 2.5 FT Raman Microscopy 2.6 Gases 2.7 Remote Sampling

73 73 74 77 77 78 79 80 82

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2.8 Alternative Lasers to NdYAG APPLICATIONS OF FOURIER TRANSFORM RAMAN SPECTROSCOPY 3.1 The Analysis of Organic Compounds 3.2 Polymers 3.3 Inorganic Materials 3.4 Surfaces 3.4.1 Catalysts 3.4.2 TLC plates 3.4.3 Metallic surfaces 3.5 Biological and Biomedical Applications 4 CONCLUSIONS 5 SOURCES OF INFORMATION 6 REFERENCES

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Chapter 4

84 84 91 93 96 97 100 100 102 103 106 106

MICRO-RAMAN SPECTROSCOPY G. Turrell and P. Dhamelincourt

1 INTRODUCTION 2 INSTRUMENTAL CONSIDERATIONS 2.1 Excitation Focusing 2.2 Collection Optics 2.3 Polarization Measurements 2.4 Confocal Microspectroscopy 2.5 Raman Imaging Techniques 2.5.1 Basic principles 2.5.2 Various mapping configurations 2.5.3 Confocal Raman line-scanning imaging 2.5.4 Modes of Operation 2.5.5 Digital image restoration 3 APPLICATIONS. 3.1 Films, Surfaces and Adsorbed Species 3.1.1 Glancing incidence 3.1.2 Integrated optics 3.1.3 Backscattering geometry 3.2 Materials Science 3.3 Geology and Environment 3.3.1 Geology 3.3.2 Environment 3.4 Biology and Medicine 3.5 The Arts 4 GONCLUSIONS 5 REFERENCES

109 110 110 112 113 116 120 120 121 123 126 126 128 128 128 128 132 134 135 135 136 136 137 140 140

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Chapter 5

Contents

HADAMARD TRANSFORM RAMAN SPECTROMETRY R.M. Hammaker, A.P. Böhlke, R.D. Freeman, J.A. Graham, J.M. Jarvis, K.J. Latas, D. Lin-Vien, A.N. Mortensen, E.A. Orr, J.D. Täte, D.C. Tilotta, J.S. White, S.L. Wright, J. V. Paukstelis and W.G. Fateley

1 BACKGROUND 2 INTRODUCTION TO HTS 2.1 The Multiplex Advantage 2.2 A Generic Description of HTS 2.3 An Example HTS System 2.4 The Hadamard Encoding Mask 2.4.1 The first generation stationary Hadamard encoding mask 2.4.2 The second generation stationary Hadamard encoding mask 2.5 Comparison of FTS and HTS for NIR Raman Spectrometry. . 3 VISIBLE HT RAMAN SPECTROMETRY 3.1 Experimental 3.1.1 The optical design of the instrument 3.1.2 The experimental arrangement 3.2 Results 3.2.1 The encodegram and spectrum 3.2.2 The spectral Observation window and resolution 3.2.3 The effect of Rayleigh line rejection on multiplexing. . 3.2.4 The application of the encoding mask as a tunable filter 3.2.5 The measurement of depolarization ratios 3.2.6 Spectral subtraction of liquids 4 THE FIRST GENERATION OF NIR HT RAMAN SPECTROMETRY 4.1 Experimental 4.1.1 Conversion from the visible to the NIR spectral region 4.1.2 Data acquisitum 4.2 Results 4.2.1 Spectra and polarization effects 4.2.2 Spectral subtraction of solids 5 THE SECOND GENERATION OF NIR HT RAMAN SPECTROMETRY 5.1 Experimental 5.1.1 Conversion from the first to the second generation of NIR HT Raman spectrometry

143 145 145 146 147 150 152 152 155 157 157 157 158 160 160 160 163 164 165 166 168 168 168 168 169 169 173 174 175 175

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5.1.2 5.2

6

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9 10 11 12

A comparison between the first and second generation stationary Hadamard encoding masks

Results 5.2.1 Polarization effects 5.2.2 Resolution 5.2.3 The multiplex advantage 5.2.4 The selective multiplex advantage QUANTITATIVE NIR HT RAMAN SPECTROMETRY IN THE ENCODEGRAM DOMAIN 6.1 Introduction 6.2 Experimental 6.3 Results STRATEGIES FOR DECREASING DATA ACQUISITION TIME USING STATIONARY HADAMARD ENCODING MASKS 7.1 Introduction 7.2 Correction of the Encodement Matrix for Temporal Systematic Errors Resulting from Failure to Reach Equilibrium 7.2.1 Introduction to temporal systematic errors 7.2.2 Experimental 7.2.3 Results 7.3 Use of Encoding Mask Temperature for Decreasing Data Acquisition Time Using Electro-optic Hadamard Encoding Masks 7.3.1 Introduction 7.3.2 Characterization of the heated PDLC mask 7.3.3 Testing of the heated PDLC mask RAMAN IMAGING AS A FORM OF MULTI-DIMENSIONAL SPECTROMETRY 8.1 Introduction to Multi-dimensional Spectrometry 8.2 Experimental 8.2.1 The 2D stationary Hadamard encoding mask 8.2.2 Instrument design for visible HT Raman imaging . . . . 8.2.3 Spatial resolution 8.2.4 Visible HT Raman imaging sample 8.2.5 Image collection 8.3 Visible HT Raman Imaging SOME SUGGESTIONS FOR THE FUTURE ACKNOWLEDGMENTS REFERENCES APPENDIX: LIST OF ABBREVIATIONS

176 178 178 180 180 182 184 184 186 187 191 191

192 192 196 196

203 203 205 205 208 208 211 211 211 212 213 213 213 217 220 221 225

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Contents

Chapter 6

SURFACE-ENHANCED RAMAN SPECTROSCOPY A. Ruperez and J.J. Laserna

1 INTRODUCTION 2 THEORETICAL BACKGROUND 2.1 Electromagnetic Mechanism 2.2 Charge Transfer Mechanism 3 METAL SUBSTRATES FOR SERS 4 INSTRUMENTAL DESIGNS SPECIFIC TO SERS 5 MOLECULAR RECOGNITION AND QUALITATIVE ANALYSIS APPLICATIONS 6 QUANTITATIVE ANALYSIS BY SERS 7 SERS IN FLOWING STREAMS: FLOW INJECTION AND LIQUID CHROMATOGRAPHIC APPLICATIONS 8 CONCLUSIONS 9 REFERENCES

227 228 228 235 240 242 248 254 259 261 261

Chapter 7 RAMAN OPTICAL ACTIVITY L. Hecht and L.D. Barron 1 INTRODUCTION 2 FUNDAMENTAL THEORY OF ROA 2.1 Light Scattering from Chiral Molecules 2.1.1 Distinction between optical rotation and ROA 2.1.2 The polarizability and optical activity tensors 2.1.3 Optical rotation in isotropic and oriented samples. . . . 2.1.4 The origin of ROA 2.2 The ROA Observables 2.3 Vibrational Raman Transition Tensors 2.4 The Bond Polarizability Theory of ROA 2.4.1 The two-group model 2.4.2 A general bond polarizability theory 2.4.3 Polarized ROA 2.4.4 Backscattered ROA 2.5 Ab Initio Calculations 3 ROA INSTRUMENTATION 3.1 General Aspects 3.2 Artefacts and Polarized ROA Measurements 3.3 Backscattering with CCD Detection: the Ultimate ROA Instrument 3.4 The Current Glasgow ROA Instruments 4 RECENT EXPERIMENTAL STUDIES OF NATURAL ROA . . . . 4.1 Tests of the Bond Polarizability Theory 4.2 Tests of the Ab Initio Theory

265 267 267 267 268 269 270 270 273 275 275 277 279 279 280 282 282 283 284 285 288 288 292

Contents

5 6 7 8

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4.3 Chiral Crystals 4.4 Biological Molecules MAGNETIC ROA ROA FROM CHIRAL SURFACES ACKNOWLEDGEMENTS REFERENCES

Chapter 8

COHERENT RAMAN SPECTROSCOPY J. Santos Gomez

1 INTRODUCTION 2 THEORY 2.1.1 Time domain nonlinear response function 2.1.2 Macroscopic nonlinear susceptibility 2.1.3 Monochromatic waves 2.1.4 Spatial symmetry 2.1.5 Quasi-monochromatic fields 2.2 Microscopic Description of the Nonlinear Susceptibility 2.2.1 Microscopic expressions for the nonlinear susceptibility 2.2.2 Raman resonances in the nonlinear susceptibility . . . . 2.3 Nonlinear Wave Propagation 3 CRS TECHNIQUES 3.1 Energy Level Diagrams 3.2 Stimulated Raman Gain and Loss Spectroscopies 3.2.1 The SRS experiment 3.3 CARS 3.3.1 The CARS experiment 3.4 Polarization Variants 3.4.1 RIKES; OHD-RIKES 3.4.2. Polarization CARS; CARS ellipsometry 4 SURVEY OF APPLICATIONS 5 REFERENCES Chapter 9

295 295 298 299 300 300

305 307 308 309 310 313 313 315 317 320 323 326 326 328 331 331 335 336 336 337 338 340

TIME-RESOLVED RESONANCE RAMAN SPECTROSCOPY M.R. Ondrias, M. C. Simpson and R. W. Larsen

1 TRANSIENT AND TIME-RESOLVED RESONANCE RAMAN SPECTROSCOPY 1.1 General Protocols for Ultrafast Resonance Raman Studies . . . 1.1.1 Transient resonance Raman (TRR) spectroscopy 1.1.2 Time-resolved resonance Raman (TRRR) spectroscopy

343 344 344 345

xii 2

3

4 5

6 7 8

Contents INSTRUMENTATION FOR TRANSIENT AND TIME-RESOLVED RESONANCE RAMAN SPECTROSCOPY... 2.1 Excitation Sources 2.1.1 Nanosecond Systems 2.1.2 Picosecond Systems 2.2 Dispersion Devices 2.3 Detectors TRANSIENT AND TIME-RESOLVED RAMAN SPECTROMETERS: REPRESENTATIVE EXAMPLES 3.1 Nanosecond Instrument 3.2 Picosecond Instrument RECENT ADVANCES IN TRANSIENT AND TIME-RESOLVED RAMAN INSTRUMENTATION SELECTED APPLICATIONS OF TRANSIENT AND TIME-RESOLVED RAMAN SPECTROSCOPY TO BIOPHYSICS AND CHEMISTRY 5.1 Nanosecond Processes 5.1.1 Ligation dynamics of hemoglobin 5.1.2 Dynamics and reactivity of chemically modined human hemoglobin 5.1.3 Transient and time-resolved resonance Raman spectroscopy of Ru(II)(L)3 complexes 5.2 Picosecond Processes 5.2.1 Time-resolved UV resonance Raman of small ring Compounds 5.2.2 Time-resolved studies of bacteriorhodopsin 5.2.3 Solvent-solute interactions 5.2.4 Excited-state structures of metalloporphyrins and hemes 5.3 Picosecond Processes with Nanosecond Pulses 5.3.1 Steady-state measurements of picosecond-scale vibrational energy redistributions SUMMARY ACKNOWLEDGMENT REFERENCES

345 346 346 346 348 349 349 349 350 353

354 354 354 355 358 363 363 366 368 372 377 378 382 383 383

Chapter 10 APPLICATIONS OF FIBER OPTICS IN NIR RAMAN SPECTROSCOPY SM. Angel, T.F. Cooney and H. T. Skinner 1 INTRODUCTION 2 THE USE OF FIBER OPTICS FOR RAMAN SPECTROSCOPY . 2.1 Setup of Fiber Optic Remote Raman Spectrometer

387 388 388

Contents

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2.2 2.3

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6

Fiber Optic Raman Probes Problems Associated with the Use of Fiber Optics for Raman Spectroscopy 2.4 Theoretical Predictions of Fiber Optic Raman Probe Performance THE USE OF NEAR-INFRARED DIODE LASERS FOR RAMAN SPECTROSCOPY 3.1 Mode Hopping 3.2 External Cavity Diode Lasers REAL-WORLD APPLICATIONS OF REMOTE RAMAN SPECTROSCOPY 4.1 Polymer Cure Monitoring 4.2 Industrial Chemical and Waste Monitoring 4.2.1 Distillation monitoring 4.2.2 Identification of solvent wastes in groundwater and soil FUTURE DEVELOPMENTS 5.1 Non-point-source Raman Probes 5.2 On-line Data Analysis REFERENCES

INDEX

392 394 404 405 406 408 408 412 412 412 415 415 417 417 421