Book contents
- Frontmatter
- Contents
- Preface
- Introduction
- 1 Radiometry
- 2 Geometrical Optics
- 3 Maxwell's Equations
- 4 Properties of Electromagnetic Waves
- 5 Propagation and Applications of Polarized Light
- 6 Interference Effects and Their Applications
- 7 Diffraction Effects and Their Applications
- 8 Introduction to the Principles of Quantum Mechanics
- 9 Atomic and Molecular Energy Levels
- 10 Radiative Transfer between Quantum States
- 11 Spectroscopic Techniques for Thermodynamic Measurements
- 12 Optical Gain and Lasers
- 13 Propagation of Laser Beams
- Appendix A
- Appendix B
- Index
9 - Atomic and Molecular Energy Levels
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Introduction
- 1 Radiometry
- 2 Geometrical Optics
- 3 Maxwell's Equations
- 4 Properties of Electromagnetic Waves
- 5 Propagation and Applications of Polarized Light
- 6 Interference Effects and Their Applications
- 7 Diffraction Effects and Their Applications
- 8 Introduction to the Principles of Quantum Mechanics
- 9 Atomic and Molecular Energy Levels
- 10 Radiative Transfer between Quantum States
- 11 Spectroscopic Techniques for Thermodynamic Measurements
- 12 Optical Gain and Lasers
- 13 Propagation of Laser Beams
- Appendix A
- Appendix B
- Index
Summary
Introduction
The emission and absorption of radiation, as well as the conversion of radiation into other modes of energy such as heat or electricity, all involve interaction between electromagnetic waves and atoms, molecules, or free electrons. Such daily phenomena as the radiative emission by the sun, the shielding of earth from harmful UV radiation by the ozone layer, the blue color of the sky, and red sunsets are all – despite their celestial magnitude – generated by microscopic particles. Most lasers depend on emission by excited atoms (e.g. the He-Ne laser), ionized atoms (the Ar+ laser), molecules (CO or CO2 lasers), impurities trapped in crystal structures (Nd: YAG or Ti:sapphire lasers), or semiconductors (GaAs diode lasers). Similarly, many scattering processes of interest (e.g., Rayleigh or Mie scattering) result from the exchange of energy and momentum between incident radiation and atomic or molecular species. In the previous chapter we saw that the energy of microscopic particles is quantized: their energy can be acquired, stored, or released only in fixed lumps called quanta. The example of the “particle in the box” (eqn. 8.19) illustrated that these energy quanta are specific not only to the particle itself but to the system to which it belongs. Thus, in the box, the energy of the particle is specified by its own mass and by the dimension of the box; in a different box, the same particle will have an entirely different system of energy levels and the quanta will have different magnitudes.
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- Information
- Introduction to Optics and Lasers in Engineering , pp. 248 - 292Publisher: Cambridge University PressPrint publication year: 1996