IR Spectoscopy - Photon Energies

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SUMMARY

The discussion centers on the conservation of energy and momentum in IR spectroscopy, specifically regarding the relationship between IR photons and phonons. It establishes that both energy, represented as ##\hbar \omega_{photon} = \hbar \omega_{phonon}##, and momentum, represented as ##\hbar k_{photon} = \hbar k_{phonon}##, must be conserved during absorption events. The conversation also touches on the implications of phonon bandgaps in relation to IR photon energies and confirms that IR spectroscopy can indeed be utilized to map the optical modes of materials.

PREREQUISITES
  • Understanding of quantum mechanics principles, particularly energy and momentum conservation.
  • Familiarity with IR spectroscopy techniques and applications.
  • Knowledge of phonon and photon interactions in solid-state physics.
  • Basic grasp of bandgap theory in materials science.
NEXT STEPS
  • Research the principles of energy and momentum conservation in quantum mechanics.
  • Explore advanced IR spectroscopy techniques for material characterization.
  • Study the role of phonons in solid-state physics and their interaction with photons.
  • Investigate the implications of bandgap sizes on IR absorption spectra.
USEFUL FOR

Researchers, physicists, and materials scientists interested in the applications of IR spectroscopy in analyzing material properties and behaviors.

Wminus
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Hi! I would like to ask some general question about IR spectroscopy.

During absorption of IR photons two quantities have to be conserved, energy ##\hbar \omega_{photon} = \hbar \omega_{phonon}## and momentum ##\hbar k_{photon} = \hbar k_{phonon}##.

Wouldn't these two quantities be conserved at the same time very rarely? I mean, what's the chances of them matching perfectly?? And what if the phonon bandgap is larger than the photons in the IR bandwidth, or much smaller?

And is it true that one can use IR spectroscopy to map out the optical modes of a material?

thanks for all replies :)
 
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