difference between excitation temperature and electron temperature in plasma
Suryasunil Rath
Both the terms are related but not the same, and they refer to different aspects of the behaviour of particles in a plasma.
Different energy states in an atom or ion correspond to different electronic configurations. The number of electrons found in each of these states is not arbitrary; it follows a statistical distribution. Excitation temperature is a way to characterize this distribution. It is a theoretical or effective temperature assigned to a Maxwellian distribution of electrons that would produce the observed population distribution among the various excited states. The Maxwell-Boltzmann distribution is a statistical distribution that describes the speeds or energies of particles in a gas (or plasma) at a given temperature. The concept of excitation temperature borrows from this distribution but is specifically applied to the distribution of electrons among excited states.
In real world, researcher, by assigning an excitation temperature, can compare the actual observed population distribution of excited states with what would be expected in a thermal equilibrium state. If the observed distribution matches the distribution predicted by a Maxwellian distribution at a certain temperature, then that temperature is considered the excitation temperature.
Electron temperature, on the other had, is a measure of average kinetic energy of electrons in a plasma that characterizes the thermal motion of electrons within the plasma. This is a crucial parameter as it influences various process and behaviour, including excitation temperature, collisional rates, ionization rates and other interactions.
Hope it helps!
I would quibble that "excitation temperature" is not a thing--excitation *energy*, however, is a thing. Electron temperature is the average energy of the electrons in a plasma; excitation energy is the energy for an electron to attain an excited state. If the electron temperature is approximately equal to the excitation energy, then statistically there will be many excited electrons, so one might loosely (and incorrectly) refer to the plasma being at the excitation temperature. Do not use that terminology, but if someone ignorant does use it, that's my guess what they mean.
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