Atomic and Molecular Spectroscopy

Atomic and molecular spectroscopy has provided basic information leading to the development of quantum mechanics and to the understanding of the building blocks of matter. It continues to provide further insight into the statics and dynamics of the microcosmos, and provides the ·means for test­ ing new concepts and computational methods. The results of atomic and molecular spectroscopy are of great importance in astrophysics, plasma and laser physics. The rapidly growing field of spectroscopic applications has made considerable impact on many disciplines, including medicine, envi­ ronmental protection, chemical processing and energy research. In particu­ lar, the techniques of electron and laser spectroscopy, the subjects of the 1981 Nobel prize in physics, have contributed much to the analytical poten­ tial of spectroscopy. This textbook on Atomic and Molecular Spectroscopy has been pre­ pared to provide an overview of modern spectroscopic methods. It is in­ tended to serve as a text for a course on the subject for final-year under­ graduate physics students or graduate students. It should also be useful for students of astrophysics and chemistry. The text has evolved from courses on atomic and molecular spectroscopy given by the author since 1975 at Chalmers University of Technology and at the Lund Institute of Technol­ ogy. References are given to important books and review articles which of different aspects of atomic and molecular allow more detailed studies spectroscopy. No attempt has been made to cover all important references, nor have priority aspects been systematically considered.

Contenu

1. Introduction.- 2. Atomic Structure.- 2.1 One-Electron Systems.- 2.2 Alkali Atoms.- 2.3 Magnetic Effects.- 2.3.1 Precessional Motion.- 2.3.2 Spin-Orbit Interaction.- 2.4 General Many-Electron Systems.- 2.5 The Influence of External Fields.- 2.5.1 Magnetic Fields.- 2.5.2 Electric Fields.- 2.6 Hyperfine Structure.- 2.6.1 Magnetic Hyperfine Structure.- 2.6.2 Electric Hyperfine Structure.- 2.7 The Influence of External Fields (hfs).- 2.8 Isotopic Shifts.- 3. Molecular Structure.- 3.1 Electronic Levels.- 3.2 Rotational Energy.- 3.3 Vibrational Energy.- 3.4 Polyatomic Molecules.- 3.5 Other Molecular Structures.- 4. Radiation and Scattering Processes.- 4.1 Resonance Radiation.- 4.2 Spectra Generated by Dipole Transitions.- 4.2.1 Atoms.- 4.2.2 Molecules.- a) Rotational Transitions.- b) Vibrational Transitions.- c) Vibrational-Rotational Spectra.- d) Electronic Transitions - The Franck-Condon Principle.- 4.3 Rayleigh and Raman Scattering.- 4.4 Raman Spectra.- 4.4.1 Vibrational Raman Spectra.- 4.4.2 Rotational Raman Spectra.- 4.4.3 Vibrational-Rotational Raman Spectra.- 4.5 Mié Scattering.- 4.6 Atmospheric Scattering Phenomena.- 4.7 Comparison Between Different Radiation and Scattering Processes.- 4.8 Collision-Induced Processes.- 5. Spectroscopy of Inner Electrons.- 5.1 X-Ray Spectroscopy.- 5.1.1 X-Ray Emission Spectroscopy.- 5.1.2 X-Ray Absorption Spectroscopy.- 5.2 Photo-Electron Spectroscopy.- 5.2.1 XPS Techniques and Results.- 5.2.2 Chemical Shifts.- 5.3 Auger Electron Spectroscopy.- 6. Optical Spectroscopy.- 6.1 Light Sources.- 6.1.1 Line Light Sources.- 6.1.2 Continuum Light Sources.- 6.1.3 Synchrotron Radiation.- 6.1.4 Natural Radiation Sources.- 6.2 Spectral Resolution Instruments.- 6.2.1 Prism Spectrometers.- 6.2.2 Grating Spectrometers.- 6.2.3 The Fabry-Pérot Interferometer.- 6.2.4 The Fourier Transform Spectrometer.- 6.3 Detectors.- 6.4 Optical Components and Materials.- 6.4.1 Interference Filters and Mirrors.- 6.4.2 Absorption Filters.- 6.4.3 Polarizers.- 6.4.4 Optical Materials.- 6.4.5 Influence of the Transmission Medium.- 6.5 Optical Methods of Chemical Analysis.- 6.5.1 The Beer-Lambert Law.- 6.5.2 Atomic Absorption/Emission Spectrophotometry.- 6.5.3 Burners, Flames, Sample Preparation and Measurements.- 6.5.4 Modified Methods of Atomization.- 6.5.5 Multi-Element Analysis.- 6.5.6 Molecular Spectrophotometry.- 6.5.7 Raman Spectroscopy.- 6.6 Optical Remote Sensing.- 6.6.1 Atmospheric Monitoring with Passive Techniques.- 6.6.2 Land and Water Measurements with Passive Techniques.- 6.7 Astrophysical Spectroscopy.- 7. Radio-Frequency Spectroscopy.- 7.1 Resonance Methods.- 7.1.1 Magnetic Resonance.- 7.1.2 Atomic-Beam Magnetic Resonance.- 7.1.3 Optical Pumping.- 7.1.4 Optical Double Resonance.- 7.1.5 Level-Crossing Spectroscopy.- 7.1.6 Resonance Methods for Liquids and Solids.- a) Nuclear Magnetic Resonance.- b) Electron Spin Resonance.- c) Electron-Nuclear Double-Resonance.- 7.2 Microwave Radiometry.- 7.3 Radio Astronomy.- 8. Lasers.- 8.1 Basic Principles.- 8.2 Coherence.- 8.3 Resonators and Mode Structure.- 8.4 Fixed-Frequency Lasers.- 8.4.1 The Ruby Laser.- 8.4.2 Four-Level Lasers.- 8.4.3 Pulsed Gas Lasers.- 8.4.4 The He-Ne Laser.- 8.4.5 Gaseous Ion Lasers.- 8.5 Tunable Lasers.- 8.5.1 Dye Lasers.- 8.5.2 Colour-Centre Lasers.- 8.5.3 Tunable Solid-State Lasers.- 8.5.4 Tunable CO2 Lasers.- 8.5.5 Semiconductor Lasers.- 8.6 Nonlinear Optical Phenomena.- 9. Laser Spectroscopy.- 9.1 Basic Principles.- 9.1.1 Comparison Between Conventional Light Sources and Lasers.- 9.1.2 Saturation.- 9.1.3 Excitation Methods.- a) Single-step excitation.- b) Multi-step excitation.- c) Multi-photon absorption.- 9.1.4 Detection Methods.- a) Fluorescence.- b) Photoionization.- c) Collisional ionization.- d) Field ionization.- 9.1.5 Laser Wavelength Setting.- 9.2 Doppler-Limited Techniques.- 9.2.1 Absorption Measurements.- 9.2.2 Intra-Cavity Absorption Measurements.- 9.2.3 Absorption Measurements on Excited States.- 9.2.4 Level Labelling.- 9.2.5 Two-Photon Absorption Measurements.- 9.2.6 Opto-Galvanic Spectroscopy.- 9.2.7 Single-Atom Detection.- 9.2.8 Opto-Acoustic Spectroscopy.- 9.3 Optical Double-Resonance and Level-Crossing Experiments with Laser Excitation.- 9.4 Time-Resolved Spectroscopy.- 9.4.1 Generation of Short Optical Pulses.- 9.4.2 Generation of Ultra-Short Optical Pulses.- 9.4.3 Measurement Techniques for Optical Transients.- a) Transient-digitizer technique.- b) Boxcar technique.- c) Delayed-coincidence techniques.- d) Streak-camera techniques.- e) Pump-probe techniques.- 9.4.4 Background to Lifetime Measurements.- 9.4.5 Survey of Methods of Measurement for Radiative Properties.- a) Linewidth measurements.- b) ODRandLC.- c) Beam-foil techniques.- d) Beam-laser techniques.- e) Time-resolved spectroscopy with pulsed lasers.- f) Time-resolved spectroscopy with pulsed electron beam excitation.- g) Phase-shift method.- h) The emission method.- i) The hook method.- 9.4.6 Quantum-Beat Spectroscopy.- 9.5 High-Resolution Laser Spectroscopy.- 9.5.1 Spectroscopy on Collimated Atomic Beams.- a) Detection through fluorescence.- b) Detection by photoionization.- c) Detection by the recoil effect.- d) Detection by magnetic deflection.- 9.5.2 Saturation Spectroscopy and Related Techniques.- 9.5.3 Doppler-Free Two-Photon Absorption.- 9.5.4 Spectroscopy of Trapped Ions and Atoms.- 10. Laser-Spectroscopic Applications.- 10.1 Diagnostics of Combustion Processes.- 10.1.1 Background.- 10.1.2 Laser-Induced Fluorescence and Related Techniques.- 10.1.3 Raman Spectroscopy.- 10.1.4 Coherent Anti-Stokes Raman Scattering.- 10.1.5 Velocity Measurements.- 10.2 Laser Remote Sensing of the Atmosphere.- 10.2.1 Optical Heterodyne Detection.- 10.2.2 Long-Path Absorption Techniques.- 10.2.3 Lidar Techniques.- 10.3 Laser-Induced Fluorescence and Raman Spectroscopy in Liquids and Solids.- 10.3.1 Hydrospheric Remote Sensing.- 10.3.2 Monitoring of Surface Layers.- 10.4 Laser-Induced Chemical Processes.- 10.4.1 Laser-Induced Chemistry.- 10.4.2 Laser Isotope Separation.- 10.5 Spectroscopic Aspects of Lasers in Medicine.- References.