For instance, assume a carbon-dioxide molecule absorbs a 2000 nm photon. Does the absorbed energy results in raised quantum energy levels in the molecule's electrons? When this molecule collides (yes, I know that it's not a collision in a hard-sphere sense) with another molecule, is there an increase in the kinetic energy of the two-molecule systems with a corresponding quantum energy decrease in the molecule that just absorbed the photon? Can you suggest references where I may find quantitative relationships about the energy conversion/transfer?


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Since this question has languished so long, it is overcome by events - namely by finding the answer myself.

Though molecular vibration is quantum, it may be approximated classically with a spring-mass system. A molecule of a particular resonant frequency can absorb a photon of the same frequency. When that occurs, the photon's energy, momentum and angular momentum are imparted to the molecule. The molecule's new translation, rotation, and vibration may be determined using energy and momentum conservation. The vibrational amplitude may be determined from residual energy after translation and rotation have been determined.

The vibrational energy may be transferred to other molecules in a gas during collisions.


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