Molecular Vibration and Translational Kinetic Energy in a Gas

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SUMMARY

The discussion centers on the vibrational energy absorption and emission characteristics of CO2 molecules, specifically at wavelengths of 2.7, 4.3, and 15 microns. It is established that CO2 does not behave like a blackbody when re-radiating energy, and the re-emission occurs at similar wavelengths to its absorption spectrum. Additionally, vibrational energy can be transferred to other molecules during collisions in a gas, potentially converting into translational kinetic energy. The interaction of vibrationally excited CO2 with other gas molecules, including H2O, suggests that energy transfer can occur beyond CO2 molecules alone.

PREREQUISITES
  • Understanding of molecular vibration and energy states
  • Knowledge of infrared absorption and emission spectra
  • Familiarity with gas dynamics and molecular collisions
  • Basic principles of thermodynamics related to energy transfer
NEXT STEPS
  • Research the infrared absorption spectra of CO2 and H2O
  • Study the principles of energy transfer in gases, focusing on vibrational and translational energy
  • Explore the concept of non-ideal gas behavior and its implications on molecular interactions
  • Investigate the role of molecular vibrations in thermodynamic processes
USEFUL FOR

Researchers in physical chemistry, atmospheric scientists, and anyone studying the thermodynamic properties of gases, particularly in relation to greenhouse gas effects and energy transfer mechanisms.

Wilko
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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?
 
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Sorry, I should have added, the gas isn't an ideal gas, it's air!
 
Have I framed my question incorrectly? Or gravely misunderstood something?
 

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