An Etymological Dictionary of Astronomy and Astrophysics

Of a gas or plasma, the temperature deduced from the → populations of atomic → excited states, as expressed by the Boltzmann formula: N_u/N_l = (g_u/g_l) exp (-ΔE/kT_ex), where N_u and N_l are the upper level and lower level populations respectively, g_u and g_l the statistical weights,
ΔE = hν the energy difference between the states,
k is → Boltzmann’s constant, and h→ Planck’s constant. The higher the energy of the occupied states, the higher the excitation temperature.

See also: → excitation; → temperature.