-----Original Message----- From: mix...@bigpond.com If lattice resonance is a factor, then some depth may be required to build up a strong enough resonance effect that the mechanism can operate. (analogous to adding more dipoles to a TV antenna)
Hi Robin, Lattice resonance and depth below the surface could be a factor. However, it is also possible that depth is counterproductive for a certain kind of resonance effect - which only works on the surface layer itself, and only with hydrogen. There is a provocative animation on the Wiki entry: http://en.wikipedia.org/wiki/Infrared_spectroscopy ... which shows an animated visualization (if you have html tuned on) of the many vibration modes that only operate at the surface layer and probably only operate with a very mobile atom like H or D. Simple diatomic molecules like deuterium, which have only one bond, may stretch and contort at high frequencies, but apparently there are large frequency gaps which are forbidden, leading to either super-radiance or sub-radiance. I have lost the citation from a few weeks ago that claimed that below a threshold of about 10 nm, the expected blackbody frequency is upshifted for nanostructures, in general. If anyone has that cite (site) handy please post it. All of these issues could overlap, based on geometry and super-radiance. In the animation above, the atoms in a CH2 group can vibrate in six different ways: stretching, scissoring, rocking, wagging and twisting. What the animation does not show is the distinct possibility of coherence (semi-coherence) in vibration - such as if these atoms (deuterons) were moving together in a tuning fork analogy. That situation would be expected to self-reinforce. If the actual frequency of vibration were to exceed the blackbody rate at the surface layer, then we might expect it to be coherent. Don't ask me why yet, but it relates to super-radiance and seems to involve atoms that are inactive in the parts of the IR spectrum unless they are stimulated by external agents. I found some published information that hydrogen fits the bill and will not emit in the IR in certain ranges - absent special circumstances. It is Russian and may not be accurate information, since it does not sound logical to me yet. More on that later. Jones
