(Montalti, Credi, Prodi, Gandolfi, Handbook of Photochemistry, third edition, p 26) Very cool if you have studied thermal radiation. Thermal radiation is basically spontaneous emission governed by planck's laws. The little snippet above shows that there should indeed be NO THERMAL FLUX deep inside of a material. I once thought that the emission would still be there, only to get re-absorbed. Not the case. If there are no modes of propagation (modes of propagation, like in a waveguide), there will be no zero-field fluctuations either. These zero-field fluctuations are the same things that produces the Casimir Effect, which states that as two plates get closer together the zero-field fluctuations between them will weaken. This leads to less force on the inside of the two plates, causing the two to accelerate towards each other.
There could very well be thermal flux arbitrarily deep within any substance. Take a cube of any material of any size. Pick two opposite faces to attach to different heat baths at different temperatures. Insulate the remaining four faces.
Well, yes! I guess there I should have said to fluctuations in molecular temperature due to spontaneous emission and re-absorption. If you take a clear glass and dope it with particles, however, these effects should persist.
But there are fluctuations in the energy levels of individual molecules to the point where a molecule has no defined temperature. Thermodynamic temperature is a statistical average which only becomes usefully descriptive for macroscopic bodies of at least several thousand atoms.
Okay, but there are differences in the amounts of energy between individual particles in the material. At any one point there should be particles in the solid with a certain amount of energy as defined by the boltzmann distribution. I suppose that inhibition of quantum fluctuations will reduce the rate at which the energy differences shift around. So, even though the the boltzmann holds whether or not there is radiative flux there will still be energy differences, but these differences will be more long-lived than those in a radiation-enhanced medium. Or, perhaps the width/ height of the boltzmann curve will be altered. .Please Register or Log in to view the hidden image!
