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A Difference between vibrational, rotational and electron temperature

  1. Feb 22, 2017 #1
    I am trying to explain the following statement in my own words...

    Would it be correct to say that..

    I am unsure if a vibrational state is simply a different energy state or something more specific?

    Do the electron temperature, vibrational temperature and rotational temperature all contribute to the overall energy state? And when it says temperature, does it mean state?

    What does "Te > Tv > Tr" tell us in regards to the properties of the plasma?

    Thanks for any help interpreting this!

    Last thing...

    How does degrees of freedom relate to the above?


    Last edited: Feb 22, 2017
  2. jcsd
  3. Feb 27, 2017 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
  4. Feb 28, 2017 #3


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    I don't know about "correct"; it would certainly be much less informative. The original is specific, yours is vague. I would say "in different energy states" rather than "vibrational or energy states", which is meaningless - vibration is not an alternative to energy. A "vibrational state" is not simply a different energy state; it is specifically a state of vibration, defined by the vibrational quantum numbers of all the vibrational modes of the molecule (only one for a diatomic like OH). Similarly a rotational state is defined by the rotational quantum numbers.
    The electronic, vibrational and rotational energy contribute to the overall energy of a molecule. Temperature is a property of an ensemble of molecules, and is related to the average energy of a molecule. Do not confuse energy with temperature - they are not the same thing.
    A "multi-temperature environment governed by particle energies" is tautologous; temperature is always governed by particle energies. The point is that there is a different distribution of energy in the different kinds of energy levels - rotational, vibrational and electronic. At thermal equilibrium the distribution of molecules between energy levels is given by the Boltzmann distribution, and if you can measure this distribution you can say what the temperature is. In a non-equilibrium situation, the "temperature" you would deduce from the observed distribution of the rotational energy levels (the "rotational temperature") may be different from the "temperature" you deduce from the observed distribution of the vibrational levels (the "vibrational temperature"), and the electronic temperature may be different again.
    I'm no expert on plasma chemistry, but in broad terms I would interpret "Te > Tv > Tr" as indicating that in the violent environment of the collapsing bubble, water molecules are torn apart to give OH radicals in excited electronic and vibrational states; in the short lifetime of the bubble these do not have time to equilibrate by collision, so the distribution of electronic states is one that would normally be characteristic of a very high (equilibrium) temperature; the distribution of the vibrational states would be characteristic of a lower temperature, and rotational lower again.
    I assume "different degrees of freedom" means rotational, vibrational or electronic energy, and the point is that you get a different T value depending on which one you look at to determine the "temperature".
  5. Mar 17, 2017 #4
    Wow, a belated thanks! Thank-you for the interpretation!
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