Modern Techniques in Applied Molecular Spectroscopy Edited by FRANCIS M. MIRABELLA Equistar Chemicals, LP A Wiley-Interscience Publication JOHN WILEY & SONS, INC. New York Chichester Weinheim Brisbane Singapore Toronto
Contents Preface List of Contributors xiii xv 1 Introduction 1 Francis M. Mirabella 1.1. Transmission Spectroscopy 4 1.2. Specular Reflectance Spectroscopy 5 1.3. Attenuated Total Reflectance Spectroscopy 5 1.4. Diffuse Reflectance Spectroscopy 6 1.5. Photoacoustic Spectroscopy 7 1.6. Infrared Microspectroscopy 7 1.7. Raman Microspectroscopy 8 1.8. Fiber Optics Techniques 9 1.9. Emission Spectroscopy 9 References 10
VI Contents 2 Transmission Infrared Spectroscopy 11 Richard W Duerst, Marilyn D. Duerst, and William L. Stebbings 2.1. History 11 Discovery of Infrared Radiation 11 Evolution of Instrumentation for Transmission Infrared Spectroscopy 13 Niche Applications 14 2.2. Principles and Theory 15 Molecular Interactions with Electromagnetic Radiation 15 Molecular Vibration-Rotation Theory 19 2.3. Instrumentation 30 Infrared Sources 30 Optical Components 34 Detectors 36 Electronics ^ 38 Mounts 38 Noise Sources 38 FFT Algorithms for FT-IR Spectrometers 39 Advantages and Disadvantages of the Different Instrument Systems 40 2.4. Experimental Considerations 41 Instrument Performance Evaluation How Do You Know If the Instrument is Functioning Properly? 41 Types of Samples, Sample Preparation Methods 42 Accessory and Methodology Choices 51 Setting up the Instrument for Sample Spectrum Collection 51 Identifying Acceptable Spectra without Artifacts 52 Data Manipulations 54 2.5. Interpretation 56 Qualitative Analysis 56 Quantitative Analysis 59 Calculated Spectra 63 2.6. Experimental Results and Case Studies 64 Water in the Gaseous State 64 Quantitative Analysis of Xylene Mixtures 67 Molecular Orientation Studies 68 2.7. Courses, Users' Groups, and Meetings 70
Contents Vll References 71 Glossary 80 3 Specular Reflection Spectroscopy 83 Robert J. Lippert, Brian D. Lamp, and Marc D. Porter 3.1. Introduction 83 3.2. Theoretical Considerations 84 Propagation of Electromagnetic Radiation through a Nonconducting Homogeneous Medium 85 Reflection of Electromagnetic Radiation at a Boundary between Homogeneous Media of Different Optical Properties 89 Band Distortions 95 Orientation Analysis 102 3.3. Experimental Considerations 104 3.4. Applications 110 Organized Thin Films 110 Redox Transformations at Electrochemical Interfaces 114 Aluminum Nitride Thin-Film Characterization 122 3.5. Conclusions and Prospectus 124 References 124 4 Attenuated Total Reflection Spectroscopy 127 Francis M. Mirabella 4.1. Introduction 127 4.2. History 128 4.3. Principles and Theory 132 4.4. Practical Considerations 142 4.5. Advantages and Disadvantages 153 Advantages 153 Disadvantages 156 4.6. Spectral Regions and Spectral Techniques Employing ATR 159 4.7. Applications of ATR Spectroscopy 160 Surface Chemistry 160 Surface Orientation 175 Specific Experimental Details 178 4.8. Conclusion 183 References 183
Vlll Contents 5 Diffuse Reflectance Spectroscopy 185 Jonathan P. Blitz 5.1. Introduction 185 5.2. Role of Diffuse Reflectance in Molecular Spectroscopy 187 5.3. Diffuse Reflectance Theory and Practice 189 Fresnel and Kubelka-Munk Reflectance 189 Kubelka-Munk Theory 192 The Practice of Diffuse Reflectance Spectroscopy 198 5.4. Applications of Diffuse Reflectance Spectroscopy 208 Diffuse Reflectance UV-Visible Spectroscopy 208 Diffuse Reflectance Near-Infrared Spectroscopy 209 Diffuse Reflectance Mid-Infrared Spectroscopy 212 5.5. Conclusions 216 References 217 6 Photoacoustic Spectroscopy 221 J. F. McClelland, S. J. Bajic, R. W. Jones, and L. M. Seaverson 6.1. Introduction 221 History and Basic Idea of PAS 222 Controllable Sampling Depth 223 Practical Uses of Controllable Sampling Depth 224 6.2. Signal Generation Theory and Data Analysis Treatments 225 Magnitude of the Photoacoustic Signal 226 Phase of.the Photoacoustic Signal 227 Photoacoustic Signal Saturation 228 Sampling Depth 230 Interpretation of Photoacoustic Signal Phase Data 232 6.3. Instrumentation 236 Photoacoustic Detector 236 FTIR Spectrometer 242 Phase Modulation 245 6.4. Applications 248 Rapid Identification of Polymers for Recycling 248 Quantitative Analysis of Major and Minor Concentrations of Additives in Paper Products 249 Analysis of Aqueous Sludges with Soluble and Insoluble Species 251 Quantitation of CaC0 3 Residual in Lime 255
Contents ix Determining Surface or Bulk Character of Polymer Additives 257 Fluorination of Polyethylene 259 Chemically Treated Polystyrene Spheres 260 Enhanced Surface Specificity by Linearization of FTIR-PAS Spectra 261 Determination of Coating Thickness from Phase Data 262 6.5. Conclusion 264 References 265 7 Infrared Microspectroscopy 267 Jack E. Katon 7.1. Historical Background 267 7.2. Infrared Microscope 270 7.3. Sampling 273 7.4. Methods of Obtaining IR Spectral Data 282 7.5. Qualitative and Quantitative Analysis of Mixtures 283 References 289 8 Raman Microspectroscopy 291 Andre J. Sommer 8.1. Introduction 291 8.2. Raman Effect 292 8.3. Signal Production and Collection 294 8.4. Instrumentation 295 8.5. Detection and Spectral Collection Mode 305 8.6. Excitation and Collection of the Raman Scattered Radiation 305 8.7. Choice of Microscope Objective 308 8.8. Sampling 310 8.9. Sampling Problems 312 8.10. Spatial Resolution 312 8.11. Sample Heating 316 8.12. Fluorescence Elimination 318 8.13. Polarization Effects 319 References 321 9 Emission Spectroscopy 323 S. Zhang, F. S. Franke, and T. M. Niemczyk 9.1. Introduction 323
X Contents 9.2. Theory 325 Blackbody Radiation 325 Real-Sample (Graybody) Radiation 329 Infrared Emission Spectroscopy of Semitransparent Thin Films 330 Stray Light 333 Emission Band Distortions 334 Temperature Determination 336 9.3. Experimental Considerations 338 Spectrometers 338 Constant Temperature IR Emission Attachments 339 Transient Infrared Emission Spectroscopy 341 Multivariate Calibration 342 9.4. Applications 343 Gas Phase Studies 343 Small Molecules on Surfaces 345 Characterization of Solid Samples 345 Atmospheric Studies 348 Planetary Observations 348 Minerals and Mineral Deposits 349 Organic Thin Films 351 Dielectric Thin Films 357 9.5. Conclusion 371 References 372 10 Fiber Optics in Molecular Spectroscopy 377 Chris W. Brown 10.1. Introduction 377 Description of Optical Fibers 377 Internal Reflection Considerations 378 Core-Cladding 379 Evanescent Wave 379 Fiber Throughput 380 10.2. Selecting Fibers 380 Optical Regions 380 Single Fibers or Bundles as Probes 384 10.3. Interfacing Fibers 386 Spectrometer Accessories 386
Contents XI Coupling Fibers to Spectrometer Accessories 387 10.4. Sampling Configuration 387 Straight-through Transmission Probes 387 Reflection-Absorption Probes 388 Evanescent Wave Probes 388 Fiber Optic Lenses 389 10.5. Applications 390 Drug Dissolution 390 Water Analysis in the Near-IR 393 Gas Analysis in the Near-IR 396 Lamination Monitoring in the Mid-IR 397 10.6. Conclusion 400 References 400 Index 403 t