- #1
Calvadosser
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My understanding is that a gas, such as CO2 for example, that interacts with electromagnetic radiation, can only absorb energy at specific frequencies, corresponding to the resonant frequencies of its molecule - equivalently the quantized energy associated with each molecular vibrational/rotational mode.
I also understand that such as gas reaches equilibrium, with equal energy in each possible mode (including kinetic energy) of its molecules [law of equipartition].
My question: If a volume of the gas is subjected to an impulse of electromagnetic energy at just one of the frequencies, F1 say, at which it absorbs radiation, then presumably immediately after it will be in a non-equilibrium state, with an excess of molecules energized at that F1.
MY QUESTION: I'd like to understand the dynamics of the gas once again reaching equipartition equilibrium. Presumably, it is actually very complicated but perhaps it can be approximated by a simple exponential curve by which the excess of molecules that have been energized at frequency F1 diminish until equilibrium is finally reached. Presumably some of the newly excited molecules will re-radiate the absorbed energy at F1 before the gas has reached equilibrium.
- Is my description correct? (Or are there misconceptions in what I have said?)
- If so, what is the approximate time constant involved?
- Does the time constant depend greatly on the temperature or the pressure of the gas? If so, how?
- What proportion of the energy at F1 absorbed from the impulse is re-radiated prior to the gas reaching equilibrium?
Thank you,
Martin
I also understand that such as gas reaches equilibrium, with equal energy in each possible mode (including kinetic energy) of its molecules [law of equipartition].
My question: If a volume of the gas is subjected to an impulse of electromagnetic energy at just one of the frequencies, F1 say, at which it absorbs radiation, then presumably immediately after it will be in a non-equilibrium state, with an excess of molecules energized at that F1.
MY QUESTION: I'd like to understand the dynamics of the gas once again reaching equipartition equilibrium. Presumably, it is actually very complicated but perhaps it can be approximated by a simple exponential curve by which the excess of molecules that have been energized at frequency F1 diminish until equilibrium is finally reached. Presumably some of the newly excited molecules will re-radiate the absorbed energy at F1 before the gas has reached equilibrium.
- Is my description correct? (Or are there misconceptions in what I have said?)
- If so, what is the approximate time constant involved?
- Does the time constant depend greatly on the temperature or the pressure of the gas? If so, how?
- What proportion of the energy at F1 absorbed from the impulse is re-radiated prior to the gas reaching equilibrium?
Thank you,
Martin