This book introduces the reader with little or no previous computer-programming experience to the Python programming language of interest for a physicist or a natural-sciences student. The book starts with basic interactive Python in order to acquire an introductory familiarity with the language, than tackle Python scripts (programs) of increasing complexity, that the reader is invited to run on her/his computer. All program listings are discussed in detail, and the reader is invited to experiment on what happens if some code lines are modified. The reader is introduced to Matplotlib graphics for the generation of figures representing data and function plots and, for instance, field lines. Animated function plots are also considered. A chapter is dedicated to the numerical solution of algebraic and transcendental equations, the basic mathematical principles are discussed and the available Python tools for the solution are presented. A further chapter is dedicated to the numerical solution of ordinary differential equations. This is of vital importance for the physicist, since differential equations are at the base of both classical physics (Newton's equations) and quantum mechanics (Schroedinger's equation). The shooting method for the numerical solution of ordinary differential equations with boundary conditions at two boundaries is also presented. Python programs for the solution of two quantum-mechanics problems are discussed as examples. Two chapters are dedicated to Tkinter graphics, which gives the user more freedom than Matplotlib, and to Tkinter animation. Programs displaying the animation of physical problems involving the solution of ordinary differential equations (for which in most cases there is no algebraic solution) in real time are presented and discussed. Finally, 3D animation is presented with Vpython.

1 The Hanle Effect and Level-Crossing Spectroscopy-An Introduction.- 1. Historical Survey.- 2. Classical Interpretation of the Hanle Effect.- 3. Quantum Mechanical Interpretation of the Hanle Effect.- 4. The Density Matrix Formalism for the Hanle Effect (Broad-Band Excitation).- 5. Laser Excitation and Pressure-Induced Coherences.- 6. Nonzero-Field Level Crossing.- 7. Conclusions.- References.- Appendix. Magnetic Effects on the Polarization of Resonance Fluorescence (original work by Wilhelm Hanle, translated by G. Moruzzi).- 2 The Hanle Effect and Atomic Physics.- 1. Introduction.- 1.1. General Expression for the Hanle Signal in Terms of the Density Matrix.- 2. Spectroscopic Applications.- 2.1. Determination of Atomic Constants.- 2.2. Measurements of Laser-Level Populations.- 2.3. Increasing Resolution, Subnatural Linewidth Effects.- 2.4. Forward Scattering, Line Crossing.- 2.5. Technical Applications.- 3. Collisions.- 3.1. Hanle Effect with Collisional Excitation.- 3.2. Hanle Effect and Optogalvanic Detection.- 3.3. Collision-Induced Hanle Resonances.- 3.4. Fluctuation-Induced Hanle Resonances.- 4. Hanle Effect in Strong Laser Fields.- 4.1. General Characteristic.- 4.2. Specific Situations.- 4.3. Hanle Effect and Nonlinear Optics.- 5. Hanle Effect in Quantum Optics.- 5.1. Dressed-Atom Model.- 5.2. Hanle Effect with Fluctuating Fields.- 5.3. Squeezing in the Hanle Effect.- References.- 3 The Hanle Effect and Level-Crossing Spectroscopy on Molecules.- 1. Introduction.- 2. Molecular Level-Crossing Signal.- 3. Comparison with Quantum Beat Experiments.- 4. Excitation of Molecules.- 5. Lifetime Investigations.- 6. Lande g-Factors.- 7. Electric-Field Level Crossing.- 8. Stark-Zeeman Recrossing and High-Field Level Crossing.- 9. Hanle Effect on NO2.- 9.1. The Influence of Detection Geometry.- 9.2. Details of the Hanle-Effect Signal.- 9.3. Collisions.- 9.4. Discussion of Hanle-Effect Experiments on NO2.- 10. Conclusion.- References.- 4 The Nonlinear Hanle Effect and Its Applications to Laser Physics.- 1. The Nonlinear Hanle Effect and Its Experimental Observation.- 2. Saturation Intensity and Saturated Linewidth.- 3. The Three-Level Case: Homogeneously Broadened Lines.- 4. The Three-Level Case: Doppler-Broadened Lines and the Rate Equations.- 5. The General Case.- 6. The Rate-Equation Approach to the Nonlinear Hanle Effect in Inhomogeneously Broadened Transitions.- 7. The Nonlinear Hanle Effect with a Gaussian Laser Beam.- 8. The Nonlinear Hanle Effect in Absorption.- 9. The Nonlinear Hanle Effect in Laser-Active Media.- 9.1. The He-Ne Laser.- 9.2. The Xe Laser.- 9.3. The He-CdII and He-ZnII Lasers.- 9.4. The Noble-Gas Ion Lasers.- 9.5. Optically Pumped Far-Infrared Lasers.- 9.6. Other Lasers.- 9.7. Conclusions.- References.- 5 Applications of the Hanle Effect in Solar Physics.- 1. Introduction.- 2. Brief Review of the Properties of Solar Magnetic Fields.- 3. Overview of the Diagnostic Possibilities and Limitations of the Hanle Effect.- 4. Basic Theoretical Concepts for Applications in Astrophysics.- 5. Diagnostics of Magnetic Fields in Solar Prominences.- 6. Survey of Scattering Polarization on the Solar Disk.- 7. Diagnostics of Turbulent Magnetic Fields.- 8. Diagnostics of Magnetic Fields in the Chromosphere-Corona Transition Region and Above.- 9. Concluding Remarks.- References.- 6 Applications of the Hanle Effect in Solid State Physics.- 1. Introduction.- 2. The Hanle Effect on Free Electrons.- 2.1. Optical Orientation of Electron Spins.- 2.2. Occurrence of Electron-Nucleus Interaction in Polarized Luminescence.- 2.3. Optical Alignment of Electron Momenta in a Magnetic Field.- 3. The Hanle Effect on Excitons.- 3.1. The ?8 x ?6 and ?7 x ?6 Excitons in Cubic Crystals.- 3.2. The ?9 x ?7 and ?7 x ?7 Excitons in Hexagonal II-VI Crystals with Wurtzite Structure.- 3.3. The ?7 x ?8 Excitons in III-VI Crystals with Symmetry Class D3h.- 3.4. The Influence of Reemission on the Hanle Effect.- 3.5. Hot Excitons and Polaritons.- 4. The H

This unique atlas presents the recorded spectrum of CH3OH, the main isotopic species of methanol, in the range 28-1258 cm-1. The spectral plot is accompanied by a list of all currently assigned rotation-torsion-vibration lines in the absorption spectrum of methanol. The list of nearly 35,000 transitions spans all of the known microwave transitions, as well as the region of coincidence with CO2 laser emissions.

I am most pleased and, in a way, I feel honored to write the Foreword for the book The Hanle Effect and Level-Crossing Spectroscopy, which covers such a very wide range of applications not only in the initial areas of atomic and molecular physics, but also in solid state physics, solar physics, laser physics, and gravitational metrology. To link these fields together in a coherent way has been the merit of the editors of the book, who attracted most distinguished authors for writing the chapters. In retrospect to Hanle's discovery of quantum mechanical coherence between two quantum states about 65 years ago, this book demonstrates the enormous impact and central importance the effect has had, and most vividly still has, on modern physics. On the other hand, the concept of quantum mechanical coherence, which is an outgrowth of the linear super position principle of quantum states, has been evident through a consider able number of experimental methods beyond the original Hanle effect; some of these methods were only recently discovered or applied and they have indeed revolutionized research fields such as atomic collision physics."

This book introduces the reader with little or no previous computer-programming experience to the Python programming language of interest for a physicist or a natural-sciences student. The book starts with basic interactive Python in order to acquire an introductory familiarity with the language, than tackle Python scripts (programs) of increasing complexity, that the reader is invited to run on her/his computer. All program listings are discussed in detail, and the reader is invited to experiment on what happens if some code lines are modified. The reader is introduced to Matplotlib graphics for the generation of figures representing data and function plots and, for instance, field lines. Animated function plots are also considered. A chapter is dedicated to the numerical solution of algebraic and transcendental equations, the basic mathematical principles are discussed and the available Python tools for the solution are presented. A further chapter is dedicated to the numerical solution of ordinary differential equations. This is of vital importance for the physicist, since differential equations are at the base of both classical physics (Newton's equations) and quantum mechanics (Schroedinger's equation). The shooting method for the numerical solution of ordinary differential equations with boundary conditions at two boundaries is also presented. Python programs for the solution of two quantum-mechanics problems are discussed as examples. Two chapters are dedicated to Tkinter graphics, which gives the user more freedom than Matplotlib, and to Tkinter animation. Programs displaying the animation of physical problems involving the solution of ordinary differential equations (for which in most cases there is no algebraic solution) in real time are presented and discussed. Finally, 3D animation is presented with Vpython.