A few days ago I wrote this about a 1989 paper in Physical Review B by a group at UC Berkeley:
What the 1989 paper did not look at was the possibility that you might be > able to excite lattice atoms into Rydberg states, where some of the > electrons have additional energy, but not enough to ionize and be ejected > from the atom. > Since then I have followed up with a question on physics.stackexchange.com, asking whether Rydberg states are possible within the bulk of a metal [1]. Ben Crowell provided an interesting response, which I think has been unfairly downvoted (without an explanation) -- I would not be surprised if he is correct. A question that was linked to my question was raised by Ron Maimon toward the end of 2012 [2]. He felt that NiH posed a challenge for his theory, as he did not know how to link the two together. He does not like the idea of p+d as the reaction behind NiH, as he thinks that critical parameters would be too small and that the rate would be too low to create a chain reaction sufficient to keep things going (see the comments to his question for a discussion). He clarified that in order for appreciable fusion to take place, the precursors must approach to within a very small distance of one another -- .0001 to .1 Angstroms. This for him ruled out any possibility of electron screening being important, as it would involve distances from .1 to 1 Angstroms, which are on the wrong scale to do anything interesting. His complaints are thought provoking. On one hand they give a better sense of the scales involved. On the other they make his specific theory less rather than more likely in my mind, for the deuterons in PdD must approach *very* close to the lattice site nuclei, which are little pinpoints in a big sea of electrons and empty space. This makes clearer the difficulty that Robin pointed out sometime back, i.e., what is it that is causing the deuterons to converge upon the lattice sites in Ron's theory? Now that I have a better mental picture of the scales involved (.0001 to .1 Angstroms), I am a little doubtful about the specific mechanism that Ron proposes. He talks about the deuterons being in banded states, but I'm not familiar enough with these to get a sense of how they are thought to work. One thing that is very nice about his theory, however, is that it provides a way to quickly dispose of the mass energy that must be dumped upon the creation of a metastable [2d]* two-deuteron resonance, or [pd]* resonance, as has been discussed here, in order to avoid the usual fusion branches and gamma rays. In Ron's account, this energy is electrostatically dumped into the palladium lattice nucleus. As a consequence, his theory implies fast 4He, and it is fast 4He that keep the reaction going. What I will now try to think about is seeing whether that energy might be dumped instead into a nearby electron in the ambient electron cloud that fills much of the volume of the metal. In this case, the daughter 4He would be nearly motionless instead of fast, and you would get a electron on the order of 24 MeV instead. That would imply lots of Bremsstrahlung, for sure. But it would also provide a way to carry the reaction forward, this time, by changing the electron charge density and increasing screening, through some as yet undetermined mechanism. The new outline leaves at least three important unknowns to be sorted out -- (a) How do the p's and d's acquire sufficient energy to fuse, even with screening? (b) What causes the electron charge distribution to change? (c) What happens to the Bremsstrahlung? Eric [1] http://physics.stackexchange.com/questions/74651/can-rydberg-states-exist-within-the-bulk-of-a-metal [2] http://physics.stackexchange.com/questions/43960/is-there-any-reproducible-tested-evidence-for-ni-h-cold-fusion
