I. Introduction.- 1. Historical Summary.- 2. Radiative Transfer Equations.- 3. Local Thermodynamic Equilibrium.- 4. Pure Scattering.- II. The Line Source Function.- 1. The General Form of SL.- 2. Steady State Equations.- 3. Specific Form of SL.- 4. An Integral Form for SL.- 5. The Form of ?
? and the Escape Probability.- 6. The Destruction Probability.- 7. Photon Random Walk, Degradation Length and Thermalization Length.- 8. Effectively Thick and Effectively Thin.- 9. The Escape Coefficient.- 10. Rate Coefficients.- 11. Free-Bound Continua.- III. The Two-Level Case: One Spectral Line.- 1. ?, r0, ?
?, and B Constant.- 2. The Influence of a Temperature Gradient.- 3. The Influence of a Gradient in ?.- 4. The Influence of a Gradient in r0.- 5. The Influence of a Gradient in ?
?.- 6. The Influence of a Moving Atmosphere.- 7. The Influence of Frequency Redistribution.- 8. The Influence of Anisotropic Scattering.- 9. The Influence of a Finite Atmosphere.- 10. The Influence of Horizontal Structure.- a. Periodic Structure.- b. The Isolated Cylinder.- c. The Imbedded Cylinder.- IV. The Multilevel Case: Two or More Lines.- 1. General Comments.- 2. Consistency Checks.- 3. Two Levels Plus Continuum.- 4. Upper Level Multiplets.- 5. Lower Level Multiplets.- 6. Metastable Levels.- 7. Two Lines in Series.- 8. Three Line Loops.- 9. Four-Line Metastable Loops.- 10. Four-Line Closed Loop.- 11. Interlocking Effects on a Strong Line of Fixed ?, r0 and ?.- 12. Discussion.- V. Line profiles.- 1. The Eddington-Barbier Relation.- 2. Depth Dependence of S
? Near Line Center.- 3. Frequency Dependence of S
?.- 4. Mapping of S? into I?.- 5. Microturbulence, Macroturbulence, and Differential Motion.- 6. Line Cores.- 7. Line Wings.- 8. Center-Limb Effects.- 9. Profile Synthesis.- 10. A Standard Set of Data.- 11. Evaluation of ??D from Cores of Strong Lines - One ? Position.- 12. Evaluation of ??D from Cores of Strong Lines - Center-Limb Data.- 13. Analysis of Line Wings.- 14. Analysis of Line Shoulders.- 15. Comments on Weak and Moderately Strong (Photospheric) Lines.- 16. A Test for LTE Using Equivalent Widths.- 17. Comparisons of Empirically Derived Line Source Functions to the Continuum Source Function.- 18. Analysis and Restoration of Line Profile Data.- VI. Total Intensities of Lines.- 1. Introduction.- 2. Curve-of-Growth for Absorption Lines.- 3. Emission Line Fluxes.- 4. The Two Level Atom.- 5. Upper Level Doublets.- 6. Lower Level Doublet and Metastable Level.- 7. Three Line Loop.- 8. Added Comments.- VII. The Line Blanketing Effect.- 1. Definition of Terms.- 2. Historical Summary.- 3. Mathematical Derivation of Blanketing Terms.- 4. The c Term.- 5. The t Term.- 6. Integrated Quantities.- 7. Influence on Temperature Structure.- 8. Multilevel Effects.- 9. Early Stellar Types.- 10. The Solar Case.- 11. The Cayrel Mechanism.- VIII. Numerical Methods.- 1. Introduction.- 2. The Integral Flux-Divergence Equations.- 3. Required Frequency Bandwidth.- 4. Frequency Mapping.- 5. Free-Bound Continua.- 6. Simultaneous Solution of the Integral Flux-Divergence Equations.- 7. A Differential Equation Method.- 8. Extension to the Multilevel Case and Linearization.- 9. Core Saturation Method.- Index of Subjects.

The usual book on the theory of spectral line formation begins with an in-depth dis­ cussion of radiation transfer, including the elegant methods of obtaining analytical solutions for special cases, and of the physics of line broadening. Neither of those features will be found in this book. It is assumed that the reader is already familiar with the essentials of transport theory and of line broadening and is ready to investi­ gate some of the particular applications of the theory to the flow of line photons through the outer layers of a star, or other tenuous media. The main thrust of this book is toward the compilation and presentation of a vast quantity of computational material available to the author in the form of computer output. The material presented represents a highly filtered sample of the published work in this subject plus an extensive set of previously unpublished results. To present large quantities of computer output in an intelligible and efficient way is a difficult task, for which I have found no really satisfactory solution. Chapters III and IV, in particular, contain almost exclusively this type of presentation. The reader may find these chapters somewhat tedious because of the level of condensation of the material. I have tried to reach a reasonable balance between over condensation and excessive detail, which in the long run may be irrelevant.