Vibrational Energy

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Shirley Wong 2E
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Vibrational Energy

Postby Shirley Wong 2E » Mon Jan 11, 2016 1:05 am

Why is vibrational contribution to the internal energy insignificant at ordinary temperatures compared to translational and rotational?

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Re: Vibrational Energy

Postby Chem_Mod » Mon Jan 11, 2016 3:11 am

To activate any energetic mode, the value kT (k = boltzmann's constant) must be at least around the ballpark of the energy gap. For translations and rotations, this energy gap is very very small and kT easily surpasses it. However, the vibrational energy gap between ground state and first excited state is relatively large (the reason for this requires quantum mechanics to explain). kT will not surpass this gap until T is maybe several hundred or thousand Kelvin.

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