Chemical Forums
Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: Lewis R on February 12, 2009, 11:26:39 PM
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It is well known that thermal vibrations of molecules produce thermal radiation or photons (infrared and visible); but in which directions?
I can understand in a gas or liquid the molecules will be rotating in all directions somewhat uniformly and, thus, photon emission will be uniform in all directions (diffuse).
But in a solid or crystal, with the molecules being restrained somewhat, would not the photon emission be in preferred directions?
Specifically, construct a simple capacitor - two metal plates separated by a dielectric material. The dielectric material will emit thermal photons in a diffuse manner from its surfaces not covered by the metal plates (i.e. from the edges of the capacitor). If a low DC voltage (up to 100 volts) is applied to the plates, will the dielectric molecules align with the electric field and, thus, emit thermal photons in a more concentrated manner, hopefully parallel to the metal plates? And what dielectric would be best for this result?
Thanks