The Electron Capture Detector and The Study of Reactions With Thermal Electrons

E. C. M. CHEN is Professor Emeritus in the Department of Natural and Applied Sciences at the University of Houston-Clear Lake. E. S. CHEN is formerly of the Center for Research on Parallel Computation at Rice University in Houston, Texas.

Foreword xiii

Preface xv

1. Scope and History of the Electron 1

1.1 General Objectives and Organization 1

1.2 General Scope 2

1.3 History of the Electron 4

References 6

2. Definitions, Nomenclature, Reactions, and Equations 8

2.1 Introduction 8

2.2 Definition of Kinetic and Energetic Terms 8

2.3 Additional Gas Phase Ionic Reactions 15

2.4 Electron Affinities from Solution Data 16

2.5 Semi-Empirical Calculations of Energetic Quantities 17

2.6 Herschbach Ionic Morse Potential Energy Curves 18

2.7 Summary 19

References 20

3. Thermal Electron Reactions at the University of Houston 22

3.1 General Introduction 22

3.2 The First Half-Century, 1900 to 1950 23

3.3 Fundamental Discovery, 1950 to 1960 25

3.4 General Accomplishments, 1960 to 1970 27

3.4.1 Introduction 27

3.4.2 The Wentworth Group 28

3.4.3 Stable Negative-Ion Formation 28

3.4.4 Dissociative Thermal Electron Attachment 33

3.4.5 Nonlinear Least Squares 35

3.5 Milestones in the Wentworth Laboratory and Complementary Methods, 1970 to 1980 37

3.6 Negative-Ion Mass Spectrometry and Morse Potential Energy Curves, 1980 to 1990 40

3.7 Experimental and Theoretical Milestones, 1990 to 2000 41

3.8 Summary of Contributions at the University of Houston 42

References 43

4. Theoretical Basis of the Experimental Tools 47

4.1 Introduction 47

4.2 The Kinetic Model of the ECD and NIMS 47

4.3 Nondissociative Electron Capture 50

4.4 Dissociative Electron Attachment 59

4.5 Electron Affinities and Half-Wave Reduction Potentials 64

4.6 Electron Affinities and Ionization Potentials of Aromatic Hydrocarbons 66

4.7 Electron Affinities and Charge Transfer Complex Energies 67

4.8 Summary 71

References 73

5. Experimental Procedures and Data Reduction 75

5.1 Introduction 75

5.2 Experimental ECD and NICI Procedures 76

5.3 Reduction of ECD Data to Fundamental Properties 85

5.3.1 Introduction 85

5.3.2 Acetophenone and Benzaldehyde 86

5.3.3 Benzanthracene, Benz[a]pyrene, and 1-Naphthaldehyde 87

5.3.4 Carbon Disulfide 89

5.3.5 Nitromethane 90

5.3.6 Consolidation of Electron Affinities for Molecular Oxygen 91

5.4 Reduction of Negative-Ion Mass Spectral Data 93

5.5 Precision and Accuracy 96

5.6 Evaluation of Experimental Results 97

5.7 Summary 101

References 101

6. Complementary Experimental and Theoretical Procedures 103

6.1 Introduction 103

6.2 Equilibrium Methods for Determining Electron Affinities 105

6.3 Photon Techniques 110

6.4 Thermal Charge Transfer Methods 116

6.5 Electron and Particle Beam Techniques 121

6.6 Condensed Phase Measurements of Electron Affinities 124

6.7 Complementary Theoretical Calculations 125

6.7.1 Atomic Electron Affinities 126

6.7.2 Polyatomic Molecules 128

6.8 Rate Constants for Attachment, Detachment, and Recombination 132

6.9 Summary 134

References 134

7. Consolidating Experimental, Theoretical, and Empirical Data 139

7.1 Introduction 139

7.2 Semi-Empirical Quantum Mechanical Calculations 140

7.3 Morse Potential Energy Curves 150

7.3.1 Classification of Negative-Ion Morse Potentials 151

7.3.2 The Negative-Ion States of H 2 153

7.3.3 The Negative-Ion States of I 2 156

7.3.4 The Negative-Ion States of Benzene and Naphthalene 157

7.4 Empirical Correlations 161

7.5 Summary 165

References 166

8. Selection, Assignment, and Correlations of Atomic Electron Affinities 168

8.1 Introduction 168

8.2 Evaluation of Atomic Electron Affinities 169

8.3 Mulliken Electronegativities 178

8.4 Electron Affinities of Atomic Clusters 184

8.5 Summary 189

References 190

9. Diatomic and Triatomic Molecules and Sulfur Fluorides 193

9.1 Introduction 193

9.2 Diatomic Molecules 194

9.2.1 Electron Affinities and Periodic Trends of Homonuclear Diatomic Molecules 194

9.2.2 Electron Affinities and Morse Potential Energy Curves: Group VII Diatomic Molecules and Anions 197

9.2.3 Electron Affinities and Morse Potential Energy Curves: Group VI Diatomic Molecules and Anions 205

9.2.4 Electron Affinities and Morse Potential Energy Curves: Group IA and IB Homonuclear Diatomic Molecules and Anions 209

9.2.5 Electron Affinities and Morse Potential Energy Curves: NO and NO(-) 214

9.3 Triatomic Molecules and Anions 216

9.4 Electron Affinities and Morse Potential Energy Curves: Sulfur Fluorides and Anions 224

9.5 Summary 229

References 229

10. Negative Ions of Organic Molecules 234

10.1 Introduction 234

10.2 Electron Affinities and Potential Energy Curves for Nitrobenzene and Nitromethane 235

10.3 Electron Affinities Determined Using the Magnetron, Alkali Metal Beam, Photon, and Collisional Ionization Methods 238

10.3.1 Electron Affinities Determined Using the Magnetron Method 238

10.3.2 Electron Affinities Determined Using the AMB Method 240

10.3.3 Electron Affinities Determined Using Photon Methods 241

10.3.4 Electron Affinities Determined Using Collisional Ionization Methods 243

10.4 Electron Affinities Determined Using the ECD, NIMS, and TCT Methods 244

10.4.1 Electron Affinities of Aromatic Hydrocarbons by the ECD Method 244

10.4.2 Electron Affinities of Organic Carbonyl Compounds by the ECD Method 246

10.4.3 Electron Affinities of Organic Nitro Compounds the ECD and TCT Methods 253

10.5 Electron Affinities of Charge Transfer Complex Acceptors 257

10.6 Substituent Effect 261

10.7 Summary 263

References 263

11. Thermal Electrons and Environmental Pollutants 266

11.1 Introduction 266

11.2 Alkyl Halides 267

11.2.1 Morse Potential Energy Curves 267

11.2.2 Experimental Activation Energies 269

11.2.3 Alkyl Fluorocompounds 272

11.2.4 Electron Affinities of the Alkyl Halides 274

11.3 Aromatic Halides 276

11.3.1 Electron Affinities of Fluoro- and Chlorobenzenes 276

11.3.2 Electron Affinities from Reduction Potentials and CURES-EC 283

11.3.3 Negative-Ion Mass Spectra and Electron Affinities 284

11.4 Negative-Ion Mass Spectrometry 287

11.5 Calculation of the ECD and NIMS Temperature Dependence 291

11.6 Summary 293

References 293

12. Biologically Significant Molecules 296

12.1 Introduction 296

12.2 Electron Affinities of Purines and Pyrimidines 299

12.2.1 Predictions of Electron Affinities 299

12.2.2 Electron Affinities from Reduction Potentials 300

12.2.3 Gas Phase Measurements of Electron Affinities 302

12.2.4 Theoretical Electron Affinities 305

12.3 Electron Affinities of Biological Molecules from Reduction Potentials 307

12.4 Gas Phase Acidities of Nucleic Acids 310

12.5 Morse Potential Energy Curves for Thymine and Cytosine 311

12.6 Gas Phase Acidities and Electron Affinities of the Amino Acids 315

12.7 The Calculation of the ECD and NIMS Temperature Dependence 316

12.8 Electron Affinities of AT AU and GC 318

12.9 Radiation Damage in DNA 320

12.10 Summary 326

References 327

Appendices 329

I Glossary of Terms, Acronyms, and Symbols 331

II Structures of Organic Molecules 336

III General Least Squares 339

IV Tables of Evaluated Electron Affinities 349

Table A.1 Atoms 349

Table A1.2 Main Group Homonuclear Diatomic Molecules 351

References 352

Table A2.1 and A.2 CH Molecules 355

References 357

Table A2.3 and A2.4 CHX Molecules 357

References 359

Table A3.1 and A3.2 CHNX Molecules 360

References 361

Table A4.1 and A4.2 CHO Molecules 362

Table A4.3 and A4.4 CHOX Molecules 366

References 369

Table A5.1 and A5.2 CHON Molecules 370

Table A5.3 and A5.4 CHONX Molecules 375

References 376

Table A6.1 Bergman Dewar set 377

Table A6.2 Values Different from NIST Values (from Tables A2.1 to A5.4) 378

Table A6.3 Unpublished or Updated Gas Phase Values not in NIST Tables 380

Table A6.4 Values for Adenine, Guanine, Cytosine, Uracil, Thymine, and Their Hydrates 382

Table A6.5 Values for Charge Transfer Complex Acceptors not in NIST Tables 382

Table A6.6 Values for Chlorinated Hydrocarbons from Reduction Potentials and CURES-EC 383

Table A6.7 Values for Biological Compounds from Reduction Potentials 383

Author Index 387

Subject Index 395