© Daniel Kleppner.
This energy level diagram shows the first five energy levels of a quantum mechanical harmonic oscillator. This type of diagram typically shows the potential energy curve (blue line) with lines (red) indicating the amount of energy each level has. The vertical axis, which is not explicitly drawn here, represents increasing energy. As this diagram shows, harmonic oscillator energy levels are evenly spaced. Equal spacing of energy levels occurs only in the harmonic oscillator. (Unit: 5)