Book contents
- Frontmatter
- Contents
- Preface to Part 1
- Preface to Part 2
- Preface to the combined volume
- 1 General introduction – author to reader
- PART 1 THE SIMPLE CLASSICAL VIBRATOR
- PART 2 THE SIMPLE VIBRATOR IN QUANTUM MECHANICS
- 13 The quantized harmonic vibrator and its classical features
- 14 Anharmonic vibrators
- 15 Vibrations and cyclotron orbits in two dimensions
- 16 Dissipation, level broadening and radiation
- 17 The equivalent classical oscillator
- 18 The two-level system
- 19 Line broadening
- 20 The ammonia maser
- 21 The family of masers: from laser to travelling-wave oscillator
- Epilogue
- References
- Index
14 - Anharmonic vibrators
Published online by Cambridge University Press: 13 January 2010
- Frontmatter
- Contents
- Preface to Part 1
- Preface to Part 2
- Preface to the combined volume
- 1 General introduction – author to reader
- PART 1 THE SIMPLE CLASSICAL VIBRATOR
- PART 2 THE SIMPLE VIBRATOR IN QUANTUM MECHANICS
- 13 The quantized harmonic vibrator and its classical features
- 14 Anharmonic vibrators
- 15 Vibrations and cyclotron orbits in two dimensions
- 16 Dissipation, level broadening and radiation
- 17 The equivalent classical oscillator
- 18 The two-level system
- 19 Line broadening
- 20 The ammonia maser
- 21 The family of masers: from laser to travelling-wave oscillator
- Epilogue
- References
- Index
Summary
We begin with some examples of one-dimensional vibration in a nonparabolic potential chosen to permit complete analytical solution of Schrödinger's time-independent equation. These examples are of isochronous vibrators which classically have a frequency independent of amplitude, and which might be expected therefore to have energy levels equally spaced at a separation of ħω0. This expectation turns out to be very nearly right and inspires a certain confidence in the semi-classical procedure developed by (among others) Bohr, Wilson and Sommerfeld. We therefore apply this procedure to some non-isochronous systems and find once more rather good agreement with the results of exact quantum mechanics. Periodic systems in fact can often be treated semi-classically with adequate accuracy, and significant economy of effort in comparison with strict quantum-mechanical analysis. This approach pays handsomely when we turn in the next chapter to the quantization of electron cyclotron orbits which, as already discussed in chapter 8, are closely related to harmonic oscillators. Conduction electrons in semi-conductors, and still more in metals, have their behaviour modified by the lattice through which they move, and a complete quantal treatment has never been achieved. It is clear, however, from approximate calculations, often of great complexity, that the semiclassical method describes most of the interesting physical processes correctly and very simply. In chapter 15 we shall describe in outline some of the effects which can be treated quite well enough for most purposes without even writing down Schrödinger's equation.
- Type
- Chapter
- Information
- The Physics of Vibration , pp. 452 - 466Publisher: Cambridge University PressPrint publication year: 1989