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Molecular Vibration and Translational Kinetic Energy in a Gas

  1. Nov 30, 2009 #1
    I understand that CO2 molecules absorb infrared at 2.7, 4.3 and 15 microns, this makes them become vibrationally excited (rocking, stretching, bending, I don't know all the modes).

    I have a few questions from this point:

    1. When the CO2 molecule re-emits that energy is it obliged to do so at wavelengths similar to its absorption spectrum; I had assumed so but I don't know for certain that this is the case despite googling the hell out of it. CO2 does not behave in anyway like a blackbody when it re-radiates, correct?

    2. In a gas, can the vibrational energy be passed from the CO2 molecule to other molecules during collisions, or can it only pass on as radiation? I understand there's a lattice effect in solids, but I don't think its relevant in a gas. Can molecular vibration 'turn into' translational kinetic energy?

    3. Assuming that the CO2 molecule re-radiates at 2.7, 4.3 and 15 microns, I imagine that H20 may 'feel' that radiation at 4.3 microns, but I guess what I'm really asking is, can vibrationally excited CO2 molecules, do work on the rest of the molecules in the gas? Or is the vibrational energy of a CO2 molecule limited to doing work on other CO2 molecules?
  2. jcsd
  3. Nov 30, 2009 #2
    Sorry, I should have added, the gas isn't an ideal gas, it's air!
  4. Nov 30, 2009 #3
    Have I framed my question incorrectly? Or gravely misunderstood something?
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