Atoms in Astrophysics

by P. Burke (Editor)

Overview

It is hard to appreciate but nevertheless true that Michael John Seaton, known internationally for the enthusiasm and skill with which he pursues his research in atomic physics and astrophysics, will be sixty years old on the 16th of January 1983. To mark this occasion some of his colleagues and former students have prepared this volume. It contains articles that de­ scribe some of the topics that have attracted his attention since he first started his research work at University College London so many years ago. Seaton's association with University College London has now stretched over a period of some 37 years, first as an undergraduate student, then as a research student, and then, successively, as Assistant Lecturer, Lecturer, Reader, and Professor. Seaton arrived at University College London in 1946 to become an undergraduate in the Physics Department, having just left the Royal Air Force in which he had served as a navigator in the Pathfinder Force of Bomber Command. There are a number of stories of how his skill with instruments and the precision of his calcula­ tions, later to be so evident in his research, saved his crew from enemy action, and on one occasion, on a flight through the Alps, from a collision with Mount Blanc that at the time was shrouded in clouds.

Product Details

ISBN-13:	9781461335382
Publisher:	Springer US
Publication date:	11/12/2011
Edition description:	1983
Pages:	356
Product dimensions:	5.98(w) x 9.02(h) x 0.03(d)

Table of Contents

1. Low-Energy Electron Collisions with Complex Atoms and Ions.- 1. Introduction.- 2. Theory of Electron Collisions with Atoms and Ions.- 2.1. Expansion of the Collision Wave Function.- 2.2. Expansion of the Target Wave Function.- 2.3. Variational Principles and the Derivation of the Coupled Integro-Differential Equations.- 2.4. Derivation of the Cross Section.- 2.5. Inclusion of Relativistic Effects.- 2.5.1. Use of the Breit—Pauli Hamiltonian.- 2.5.2. Use of the Dirac Hamiltonian.- 3. Numerical Solution of the Coupled Integro-Differential Equations.- 3.1. Early Work.- 3.1.1. Iterative Methods.- 3.1.2. Reduction to a System of Coupled Differential Equations.- 3.2. Reduction to a System of Linear Algebraic Equations.- 3.3. R-Matrix Method.- 3.4. Matrix Variational Method.- 3.5. Noniterative Integral Equations Method.- 3.6. New Directions.- 3.7. Illustrative Results.- 4. Computer Program Packages.- 4.1. Structure Packages.- 4.2. Collision Packages.- References.- 2. Numerical Methods for Asymptotic Solutions of Scattering Equations.- 1. Introduction.- 2. Specification of Asymptotic Forms.- 3. Travels in Intermedia.- 3.1. Numerical Integration of the Differential Equations.- 3.2. Noniterative Integration of the Phase-Amplitude Equations.- 4. At the Border of Asymptopia.- 4.1. Asymptopic Expansions.- 4.2. Iterative Techniques.- 4.2.1. The Iterated WBK (IWBK) Method.- 4.2.2. The Generalized Matricant.- 5. Concluding Remarks.- References.- 3. Collisions between Charged Particles and Highly Excited Atoms.- 1. Introduction.- 2. The Impact Parameter (IP) Method.- 3. The Sudden Approximation.- 4. Transitions between Levels with Quantum Defects.- 5. Transitions within the Degenerate Sea.- References.- 4. Proton Impact Excitation of Positive Ions.- 1. Introduction.- 2. Excitation of Fine-Structure Transitions.- 2.1. Semiclassical Theory.- 2.2. Quantal Theory.- 3. Excitation of Metastable Transitions.- 4. Charge-Transfer Ionization.- References.- 5. Long-Range Interactions in Atoms and Diatomic Molecules.- 1. Introduction.- 2. General Form of the Model Hamiltonian.- 3. Form of the Model Potential for Atomic Systems.- 3.1. The Exact Interaction between the Valence Electrons and the Core.- 3.2. Second-Order Perturbation Theory: The Static Contribution.- 3.3. The First Nonadiabatic Correction.- 3.4. The Second Nonadiabatic Correction.- 3.5. Nonadiabatic Corrections of Higher Order.- 3.6. Third-Order Perturbation Theory: The Static Contributions.- 3.7. Summary of Results.- 4. Form of the Model Potential for Diatomic Systems.- 4.1. The Exact Interaction between the Valence Electrons and the Cores.- 4.2. Second-Order Perturbation Theory: The Static Contributions.- 4.3. The First Nonadiabatic Correction.- 4.4. The Second Nonadiabatic Correction.- 4.5. Nonadiabatic Corrections of Higher Order.- 4.6. Third-Order Perturbation Theory: The Static Contribution.- 4.7. Summary of Results and the Separated Atom Limit.- 5. Addition Theorems for Solid Harmonics.- References.- 6. Applications of Quantum Defect Theory.- 1. Historical Survey.- 2. Mathematical Background to Quantum Defect Theory.- 2.1. Properties of Coulomb Wave Functions.- 2.2. Solutions of the Coupled Equations.- 2.2.1. All Channels Closed.- 2.2.2. Some Channels Open.- 3. Single-Channel Quantum Defect Methods: General Formulas in the Independent-Particle Approximation.- 3.1. Expressions for the Wave Functions.- 3.2. General Formulas for Radiative Transition Probabilities.- 3.3. Collision Cross Sections.- 3.3.1. Use of Extrapolated Quantum Defects.- 3.3.2. Use of Adjusted Calculated Quantum Defects.- 3.3.3. Use of Observed Quantum Defects in the Bethe Approximation.- 3.4. Summary.- 4. Applications to Simple Multichannel Problems.- 4.1. The Spectrum of Calcium.- 4.1.1. Bound States.- 4.1.2. Autoionizing States.- 4.2. Bound States of Complex Ions by Extrapolation of Calculated Scattering Parameters: Configurations 1s22s22pqnl.- 4.3. The Spectrum of the H2 Molecule.- 5. Extrapolation of the Generalized Reactance Matrix.- 5.1. Discussion of Extrapolation Methods.- 5.1.1. Restrictions on the Validity of Extrapolation Methods.- 5.1.2. Fitting Techniques.- 5.2. Applications.- 5.2.1. Collision Strengths in LS-Coupling.- 5.2.2. Collision Strengths for Excitations between Fine-Structure Levels.- 5.2.3. Photoionization Gross Sections.- 5.2.4. Electron Impact Ionization Cross Sections.- 6. Conclusions.- References.- 7. Electron-Ion Processes in Hot Plasmas.- 1. Introduction.- 2. Line Intensities.- 2.1. Level Populations.- 2.2. Forbidden Lines.- 2.3. Satellite Lines.- 3. Electron-Ion Processes.- 3.1. Introduction.- 3.2. The A+z + e System.- 3.3. Coupling between Open Channels.- 3.4. Resonance Contribution to Collisional Excitation.- 3.5. Approximate Methods for Strong Allowed Transitions.- 3.6. Relativistic Effects.- 3.7. Relativistic Effects in Autoionization.- 4. Conclusion.- A.1. Derivation of am(E) and b?i(E).- A.2. Resonances.- A.3. Gailitis Formula.- References.- 8. The University College Computer Package for the Calculation of Atomic Data: Aspects of Development and Application.- 1. Introduction.- 2. The Growth of Astronomical Observations.- 3. Some Aspects of the Genesis of the Programs.- 4. The C III Challenge.- 4.1. Collision Strengths and Transition Probabilities for the Interpretation of the Solar Spectrum.- 4.2. Excitation of C III by Recombination.- 4.2.1. Observations.- 4.2.2. Rate Coefficients from Detailed Balance Arguments.- 4.2.3. Improved Low-Temperature Coefficients.- References.- 9. Planetary Nebulae.- 1. Introduction.- 2. Observations.- 2.1. Optical.- 2.2. Infrared.- 2.3. Radio.- 2.4. Ultraviolet.- 2.4.1. NGC 7662.- 2.4.2. IC 418.- 2.4.3. The C/O Ratio in Planetary Nebulae.- 3. Models: Atomic Data.- 3.1. Charge Transfer.- 3.1.1. O+.- 3.1.2. O2+.- 3.1.3. Ne2+.- 3.2. Dielectronic Recombination.- 3.3. Photoionization and Radiative Recombination.- 3.4. Electron Collisional Excitation.- 3.5. Radiative Transition Probabilities.- References.- 10. Forbidden Atomic Lines in Auroral Spectra.- 1. Introduction.- 2. Beginnings.- 3. Seaton’s Work.- 4. Refinement of Classical Theory.- 5. Advent of In Situ Measurements.- 6. N2(A3?u+)—O Excitation Transfer.- 7. Quenching.- 8. Coordinated Rocket and Satellite Measurements.- 9.—3466 and—10,400 of N I.- References.