Theory of Unimolecular Reactions

1st Edition - January 28, 1973
Author: Wendell Forst
Language: English
eBook ISBN:
9 7 8 - 0 - 3 2 3 - 1 4 9 3 5 - 8

Theory of Unimolecular Reactions provides a comprehensive analysis of the theory of unimolecular reactions, also known to kineticists as the Rice-Marcus or the… Read more

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Theory of Unimolecular Reactions provides a comprehensive analysis of the theory of unimolecular reactions, also known to kineticists as the Rice-Marcus or the Rice-Ramsperger-Kassel-Marcus theory, and to those working in mass spectrometry and related fields as the quasi-equilibrium theory or the theory of mass spectra. This book demonstrates how theoretical parameters are related to experimental observables and describes the methods that are used to obtain useful numerical answers. This monograph consists of 11 chapters and begins by explaining the derivation of the expression for the basic rate k(E), with emphasis on the unimolecular rate constant, intramolecular energy transfer, and potential energy surfaces in unimolecular reactions. The statistical calculation of unimolecular rate under vibrational potential is also given, along with pertinent degrees of freedom. The remaining chapters explore the energy distribution functions appropriate to each system, the averaging of k(E), and the relations between theoretical and experimental parameters. Thermal reactions, chemical activation systems, and the theory of mass spectra are examined. The last chapter is devoted to the transition state and its ambiguities. This text will be of interest to gas kineticists, mass spectrometrists, and students and researchers working in the field of physical chemistry.

Foreword

Preface

Acknowledgments

Part I Introduction

Chapter 1. The Unimolecular Rate Constant

1. The Unimolecular Process

2. Decay of a Pure Bound State into a Single Channel

3. Average Rate

4. Average Lifetime

5. Basic Assumption

Exercises

References

Chapter 2. Intramolecular Energy Transfer

1. Theory of Slater

2. Theory of Rice, Ramsperger, and Kassel

3. Intramolecular Energy Transfer

4. Randomization of Energy and Experimental Evidence

5. Theoretical Treatment of Energy Randomization

6. The Rice-Marcus (RRKM) Theory

References

Chapter 3. Potential Energy Surfaces in Unimolecular Reactions

1. Triatomic Potential Energy Surface for a Vibrational Potential

2. Triatomic Potential Energy Surfaces for an Effective Potential

3. Triatomic Potential Energy Surfaces for Nonadiabatic Reactions

4. Extrapolation to Polyatomic Potential Energy Surfaces

References

Chapter 4. Statistical Calculation of Unimolecular Rate under Vibrational Potential

1. Unimolecular Process in Classical Phase Space

2. The Quantum-Mechanical Unimolecular Rate Constant

3. An Alternative Derivation

4. Nonclassical Effects Near Potential Barrier Maximum

5. Reaction Path Degeneracy

Exercises

References

Chapter 5. Pertinent Degrees of Freedom

1. Degrees of Freedom Excluded by Conservation Requirements

2. Internal Degrees of Freedom

3. External Degrees of Freedom

4. Model for Particle

References

Chapter 6. Calculation of Energy-Level Densities

1. Terminology and Basic Concepts

2. Direct Evaluation of W(E) and G{E) in Simple Systems

3. Approximation to N(E) and G(E): General Considerations

4. Inversion of the Partition Function

5. Approximation to N(E) and G(E) for Rotational States

6. Direct Evaluation of Nvr(E) and Gvr(E) in Simple Systems

7. Approximations Based on Inversion of Classical Partition Function

8. Approximations Based on the Inversion of the Quantum-Mechanical Partition Function

9. Approximation to Nvr(E) and Gyr(E) for more Realistic Systems

10. Conclusions

Exercises

References

Chapter 7. Unimolecular Rate with an Effective Potential

1. The Rotational Potential

2. Type 1 Vibrational Potential

3. Effective Potential for Type 1 Reaction

4. Effective Potential for Type 2 and Type 3 Reactions

Exercise

References

Part II Introduction

Chapter 8 Thermal Reactions

1. Collisional Activation: General Features of Lindemann's Simple Mechanism

2. Averaging over Equilibrium Distribution

3. Averaging over Steady-State Distribution

4. Evaluation of Centrifugal Correction Factors

5. Pressure Dependence

6. Temperature Dependence

7. Theoretical Parameters and Experimental Observables

8. Generalized Lindemann's Mechanism and the Nonequilibrium Distribution

Exercises

References

Chapter 9 Chemical Activation Systems

1. Nature of Chemical Activation

2. Determination of the Energy Distribution Function

3. Pressure Dependence of Rate

4. Temperature Dependence of Rate

5. Collisional Deactivation in a Multilevel System

6. Photo-activation

7. Theoretical Parameters and Experimental Observables

8. Centrifugal Effects

Exercises

References

Chapter 10 Fragmentation of Highly Excited Species: Theory of Mass Spectra

1. Unimolecular Reactions of Positive Ions

2. Consecutive-Parallel Reactions: Energy Partitioning

3. Production of Ionized Species

4. Potential Energy Surfaces of Polyatomic Ions

5. Randomization of Electronic Energy

6. Determination of Energy Distribution Function

7. Primary Yield in Radiolysis

8. Theoretical Parameters and Experimental Observables

9. Kinetic Energy of Fragments and Rotational Effects

Exercises

References

Chapter 11 Transition States in Unimolecular Reactions

1. General Remarks; Isotope Effect

2. Transition States for Type 1 Reactions

3. Transition States for Type 2 Reactions

4. Transition States for Type 3 Reactions

Exercises

References

Appendix

List of Symbols

Author Index

Subject Index