The monograph describes phenomena of atomic states interference and their applications to atomic spectroscopy. The theory of these phenomena is treated by means of several approaches beginning from the classical point of view and then by using more and more sophisticated considerations.

Inhalt

1. Introduction.- 2. Classical Description of Interference Phenomena in Radiation.- 2.1 The Classical Oscillator Model of Atomic Emission.- 2.2 A Classical Oscillator in a Magnetic Field.- 2.3 Emission from an Oscillator in a Magnetic Field.- 2.4 Emission from an Ensemble of Oscillators.- 2.5 Beats in Intensity.- 2.6 The Hanle Effect.- 2.7 Combination of Hanle Effect and Quantum Beats.- 2.8 Beat Resonances.- 2.9 Parametric Resonance.- 2.10 Conclusion.- 3. Quantum Mechanical Description of Interference Phenomena.- 3.1 The Density Matrix.- 3.2 Derivation of the Density Matrix of Ensembles of Excited States from the Wave Equation.- 3.3 The Equation of Motion of the Density Matrix.- 3.4 Spontaneous Emission.- 3.5 Limits of the Density Matrix Apparatus. The Scattering Matrix.- 3.6 Interference Signals.- 3.7 The Radiation Pattern and Polarization for Transitions Between Eigenstates of the Angular Momentum Operator.- 3.8 Influence of Interference Between States on the Polarization of Spontaneous Radiation.- 3.9 Redistribution of Radiated Energy Due to the Interference of Quantum States.- 3.10 Some Results from the Formalism of Irreducible Tensor Operators.- 3.11 Radiation Polarization in the Statistical Tensor Formalism Comparison of the Conclusions of Quantum Mechanical and Classical Approaches.- 3.12 Biaxial Alignment.- 3.13 Level Anti-crossings.- 3.14 Interference Phenomena in Magnetic Resonance.- 3.15 Application of Interference Signals.- 4. Experimental Observation of Interference Signals.- 4.1 Basic Experimental Scheme.- 4.2 Ensembles of Particles.- 4.3 Techniques for Inducing Coherence.- 4.4 Observation of Interference Phenomena.- 4.5 Hanle Effect in Atoms in the Ground State.- 4.6 Manifestation of the Interference of States in Collisions.- 4.7 Quantum Beats upon PulseExcitation.- 4.8 Coherent Resonances.- 4.9 Other Resonances.- 4.10 Self-Alignment of Atomic States in a Plasma.- 4.11 Hidden Alignment.- 4.12 Self-Orientation.- 4.13 Interference of Atomic States in Astrophysics.- 4.14 Cascaded Transitions.- 4.15 Diffusion of Radiation.- 4.16 Influence of the Laboratory Magnetic Field on the Hanle Signal Shape. False Hanle Signals.- 4.17 Spectral Content of the Exciting Light and Absorption Line Profile.- 4.18 Faraday Rotation.- 4.19 Hanle Effect Due to Excitation That Is Random with Time.- 4.20 Polarization of Atomic Fluorescence in a Flame.- 4.21 Detection of the Polarization Moments by Radioactivity.- 4.22 Use of the Polarization Moments for Improving the Accuracy of Nonlinear Spectroscopic Techniques.- 4.23 Conclusion.- 5. Calculation of Interference Signals.- 5.1 An Atom in a Magnetic Field.- 5.2 The Hyperfine Structure.- 5.3 The Magnetic Dipole Interaction Constant.- 5.4 Quadrupole Interaction Between a Nucleus and an Electron Shell.- 5.5 Transition Matrix Elements of the Electric Dipole Moment.- 5.6 Eigenpolarizations of Transitions.- 5.7 Matrix Elements of the Dipole Transition Between States with Hyperfine Structure.- 5.8 The Stark Effect.- 5.9 Atoms with Nonzero Nuclear Spin in External Fields.- 5.10 Perturbation Operators and Their Matrix Elements.- 5.11 The Zeeman Effect in Atoms with Hyperfine Structure.- 5.12 The PaschenBack Effect.- 5.13 Hyperfine Splitting in a Weak Magnetic Field.- 5.14 The Stark Effect in Atoms with Hyperfine Structure in a Weak Electric Field.- 5.15 The Stark Effect in Atoms with Hyperfine Structure in Intermediate Fields.- 5.16 Splitting of Atomic Levels with Hyperfine Structure in a Strong Electric Field.- 5.17 Behaviour of Atoms in Combined Fields.- References.