- The wavelength of IR light from the surface ranges from about 5 microns to about 50 microns. The space between molecules at atmospheric pressure is about a tenth of a micron. The size of a molecule is about .0002 microns.
- To explain IR by photons does not make sense. If you read my treatise on blackbody radiation or my Sky Dragon article, then you will find IR as a collective wave phenomenon involving many atoms which may give a better picture of the physics than mysterious giant photons being captured by miniscule atoms.
The idea of blackbody radiation as a collective phenomenon is also presented in the blog post
Blackbody Radiation as a Generic Emergent Phenomenon. In this perspective absorption and emission of IR cannot be explained by looking at properties of single atoms or molecules, but results from the interaction of many atoms.
The energy of IR radiation seems to be too small to result from electronic transitions.
The radiative properties of the atmosphere may thus not be explainable solely in terms of so-called greenhouse gases with specific atomic absorption/emission spectra.
The idea of photon particles as carriers of heat energy is primitive, confusing and has led to the unphysical concept of back radiation. Radiation as wave phenomenon makes much better sense.
Inlägg
You say "The energy of IR radiation seems to be too small to result from electronic transitions." This is true. IR radiation generally comes from changes in the quantum state of vibrations and rotations in molecules, not changes in electron states. The classic text on this is by German/Canadian Nobel Prize winner Gerhard Herzberg - "Molecular Spectra and Molecular Structure" (4 vols. 1939–79) I suggest you dig up a copy and read it, it's very informative on how this all actually works.
SvaraRaderaThanks for important refs.
SvaraRaderaVery interesting discussion here. I believe it's somewhat commonly understood that radio waves cannot be produced by the motion of a single electron but rather involve the motions of all electrons in the antenna. The Plasma cut off frequency of an electron is well above that of IR radiation so that, acting alone, it cannot move in such a way when interacting with fluctuating EM fields that would allow it to produce a photon.
SvaraRaderaA reprint of this 1955 classic is available at a very reasonable cost:
SvaraRaderaMolecular Vibrations: The Theory of Infrared and Raman Vibrational Spectra by Wilson, Decius and Cross
Yes its correct that infrared radiation comes from changes in the quantum state of vibrations and rotations in molecules. It's misguided to think that infrared radiation comes from changes in electron states. great article, thanks for sharing.
SvaraRadera