Rami Arieli: "The
Laser Adventure" Chapter 2.5 page 3
Population at Thermodynamic Equilibrium
Figure 2.2 shows the population of each energy level at thermodynamic
equilibrium.
Figure 2.2: Population Numbers at "Normal Population"
Attention !
Figure 2.2 (and most of the figures later in these course) plot the
energy values of the energy levels on y axis, and the corresponding population
numbers on the x axis. If we interchange the axes, we get a histogram
in which the height of each column shows the population number of each
level. The width of the energy levels in this figure is arbitrary, and
does not correspond to the real width of each level.