Case Studies in Atomic Collision Physics

Contents

Chapter 1. Three-Body Recombination of Positive and Negative Ions


1-1. Introduction to Ionic Recombination


1-2. Historical Survey

A. The Classical Theory of Thomson, and Related Theories

B. Quasi-Equilibrium and Diffusion Theories

C. Experimental Methods


1-3. Quasi-Equilibrium Statistical Theory at Low Densities

A. Formula For The Three-Body Recombination Coefficient

B. Quasi-Equilibrium Distribution


1-4. Ions Recombining in Their Parent Gas

A. Energy-Change Rate Coefficient

B. Calculation of the Recombination Coefficient

C. The Non-Thermal Effect


1-5. General Third Body

A. General Aspects of A Collision

B. Formula for the Rate Coefficient

C. Reduced Parameters and Detailed Balance

D. The Rate Coefficient For Special Cases


1-6. Calculation of the Recombination Coefficient

A. Differential Scattering Cross Sections

B. Computations

C. Partial Recombination Coefficient

D. Quasi-Equilibrium Distribution Function

E. Temperature and Interaction

F. Mass Effect


1-7. Theoretical and Experimental Three-Body Ionic Recombination Coefficient


1-8. Simple Treatment of Three-Body Ionic Recombination

A. Recombination As A Markov Process

B. Recombination Coefficient Deduced From the Diffusion, Effective-Gradient and Modified Effective-Gradient Methods


1-9. Three-Body Recombination at Moderate and High Gas-Densities

A. Natanson's Theory

B. Modification to Natanson's Theory

C. Comparison with Experiment

Appendix. The Thomson Theory

Acknowledgments

References

Chapter 2. Precision Measurements of Electron Transport Coefficients


2-1. Introduction


2-2. Theory of Electron Swarms

A. The Electron Energy Distribution Function

B. Transport Coefficients

C. The Derivation of Cross Sections From Transport Coefficients


2-3. The Electron Drift Velocity

A. Review of Previous Methods of Measurement

B. The Bradbury-Nielson Method

C. Experimental Data


2-4. The Measurement of Dt/µ by The Townsend-Huxley Method

A. Introduction

B. The Solution of the Diffusion Equation and the Current Ratio Formula

C. Experimental Method

D. Sources of Error

E. Experimental Results


2-5. Conclusion

Acknowledgments

References

Chapter 3. Differential Cross Sections in Electron Impact Ionization


3-1. Introduction


3-2. Kinematics and Notations


3-3. Different Types of Cross Sections


3-4. Choice of Target Gas and Collision Variables


3-5. The Apparatus

A. Description of the Electron Impact Spectrometer

B. Detection Electronics and Measurement Procedures

C. Intensities

D. Background Problems

E. Stray Fields

F. Modes of Operation

G. Normalization Problems


3-6. Experimental Results

A. Double Differential Cross Sections

B. The Triple Differential Cross Section


3-7. Comparison with Theory


3-8. Measurements Close to The Ionization Threshold

Acknowledgment

References

Chapter 4. Interpretation of Spectral Intensities From Laboratory and Astrophysical Plasmas


4-1. Introduction


4-2. Theoretical Methods

A. Statistical Equilibrium For Excited States

B. Effects of Metastable Levels

C Collisional Excitation

D. Levels Above The First Ionization Limit

E. Line Ratio Measurement of Electron Temperature

F. Line Ratio Measurement of Electron Density


4-3. Collision Rate Experiments

A. General Methods

B. Electron Beam Excitation

C. Laboratory Plasma Experiments

D. Theta-Pinches


4-4. Lithium-Like Ions

A. General Description

B. Energy Levels

C. Transition Probabilities

D. Collisional Excitation Rates

E. Statistical Equilibrium

F. Line Intensities in Laboratory Sources

G. Solar Line Intensities

H. Dielectronic Satellite Lines


4-5. Beryllium-Like Ions

A. General Description

B. Energy Levels

C. Transition Probabilities

D. Collisional Excitation Rates

E. Equations of Statistical Equilibrium

F. Laboratory Plasmas

G. Solar Line Intensities

H. Low Density Objects, Quasars, and Planetary Nebulae

I. Recent Developments


4-6. Helium-Like Ions

A. General Description

B. Energy Levels

C. Transition Probabilities

D. Collisional Excitation Rates

E. Low Density Plasmas

F. High Density Plasmas

G. Intermediate Densities

H. Line Ratios, Nₑ and Tₑ

I. Dielectronic Satellite Lines

J. Absolute Intensities

K. Recent Developments

Acknowledgements

References

Chapter 5. Atomic Processes in Astrophysical Plasmas


5-1. Introduction


5-2. Stellar Atmospheres

A. General Theory of Radiative Transfer

B. The Construction of Model Atmospheres

C. Line Radiation

D. Departures From Local Thermodynamic Equilibrium


5-3. The Continuous Spectrum

A. General Formulae

B. Absorption By Neutral Atoms and Positive Ions

C. Photodetachment of Negative Ions

D. Coherent Scattering


5-4. The Line Spectrum

A. Transition Probabilities

B. The Line Profiles - General Formulae

C. Pressure Broadening of Spectral Lines


5-5. Collisional Excitation and Ionization

A. The Quantum Mechanical Theory - General Formulae and Approximations

B. Classical and Semi-Classical Approximations


5-6. Interpretation of Observations

A. Curve of Growth Analysis

B. The Solar Atmosphere

C. The Early-Type Stars and Planetary Nebulae

D. The Late-Type Stars; Molecular Absorption

E. Stars of Non-Solar Composition


5-7. Problems Requiring Further Study

Acknowledgments

References

Chapter 6. Polarized Orbital Approximations


6-1. Introduction


6-2. The Basic Method and Notation


6-3. The Polarized Target Wave Function

A. The Adiabatic Approximation

B. Perturbation Theory

C. The One-Electron Target

D. Variational-Perturbation Methods

E. The Exact Static Solution For The One-Electron Target

F. The Many-Electron Target; Sternheimer's Approximation


6-4. The Total Polarized Orbital Wave Function and the Scattering Problem

A. Introductory Remarks

B. The Total Wave Function and Non-Variational Methods

C. Variational and Variationally Motivated Methods


6-5. Applications to Electron Scattering and Reactions

A. Scattering From One-Electron Targets

B. Scattering From Helium

C. Scattering From Other (Non-Highly Polarizable) Atoms

D. Scattering From Highly Polarizable Atomic Systems

E. Electron-Molecule Scattering

F. Photoionization, Autoionization and Ionization


6-6. Application to Positron Scattering and Annihilation

A. Positron-Hydrogen Scattering

B. Positron-Helium Scattering and Annihilation

References

Chapter 7. Photodetachment: Cross Sections and Electron Affinities


7-1. Introduction


7-2. Photodetachment Cross Sections

A. Introduction

B. Theory

C. Experiment

D. Double Photon Detachment


7-3. Photodetachment Thresholds

A. Experimental Energy Determination

B. Threshold Behavior Theory

C. Comparison of Experiment with Theory


7-4. Experimental Approaches

A. Plasma

B. Beams


7-5. Electron Affinities

A. Techniques

B. Case Study: S‾

C. A Selected List of Electron Affinities

Acknowledgment

References

Chapter 8. The Role of Metastable Particles in Collision Processes


8-1. Introduction


8-2. Production of Metastables

A. Thermal Metastables

B. Fast Metastables


8-3. Detection and Identification

A. Collisions with Surfaces

B. Collisions with Gas Atoms Or Molecules

C. Collisions with Photons

D. Collisions with Electrons

E. Interaction with D.C. Electric and Magnetic Fields

F. Magnetic Resonance Techniques


8-4. Chemiionization

A. General Principles of thermal Energy Metastable Collision Experiments

B. Absolute Measurements

C. Measurements of Singlet-Triplet Cross Section Ratios

D. Models of Chemiionization Reactions

E. Theoretical Treatments of Chemiionization

F. Chemiionization Involving Highly Excited Atoms


8-5. Ion Beam Studies

References

Author Index

Subject Index