Hydrogen-switchable mirrors

Posted November 14, 2005

Today I attended a talk about measurements of the Casimir force, which of course is a fascinating topic all by itself, but as a side point in the lecture I was introduced to the existence of hydrogen-switchable mirrors. In this phenomenon, when a thin film of certain metals is exposed to a hydrogen atmosphere, the adsorption of the hydrogen into the film creates a metal-insulator transition and alters the reflectivity of the mirror, sometimes dramatically, and reversibly.

This in itself is interesting, but what caught my eye is that one of the metals which does this is our friend palladium, often used in cold fusion experiments. In normal descriptions of that phenomenon, deuterium atoms are adsorbed into the metal lattice, wherein Weird Things happen and fusion supposedly takes place.

So, this mirror phenomenon is a good indication that hydrogen (and probably deuterium too) being adsorbed into a metal can indeed manage to trigger some manner of weird effects, at least to the extent of altering the electromagnetic characteristics of the metal enough to change its reflectivity. Could that alter things enough to provide a catalyst environment for fusion too?

The flip side, however, equally interesting, is that there are plenty of weird things happening just chemically between hydrogen and palladium, which are poorly understood and investigated still. So maybe the odd heat effects possibly seen in cold fusion experiments may have a perfectly "normal" non-fusion explanation through these sorts of effects. (This is the position I've long held, although admittedly without enough investigation into the details to justify that belief.)

The nice thing is, either outcome would be a worthwhile discovery.