There are others here with better knowledge of nuclear physics than me, since I've done theoretical physics but not specifically nuclear physics.
For D+D:
n+3He
or
1H + 3H
are both common reaction pathways and very fast indeed.
gamma + 4H is much less likely. But you cannot simply rule out some alteration in reaction pathway probability in different circumstances, though those circumstances can only be local electric and magnetic fields, and (major influence) D-D collision energy. (Maybe someone can think of something else).
It seems plausible that gamma emission from the unstable 4He + added energy nucleus would be much slower than the two above splits - but I don't know anything about this I'm afraid.
One issue with LENR, and one that makes me suspicious, is that there really is no good agreement about what reaction is ocurring. While D+D with some mechanism that strongly favoured gamma+4He over other pathways is what some proponents suggest, the large number who claim p+e-> n, then neutron capture by anything in sight, or p+Ni-> something have incompatible hypotheses of LENR. So you cannot group together all the evidence. I've not seen any hypothesis that accounts properly for all of the claimed anomalies, or even most of them.
And I also suspect that 4He + gamma is a favoured reaction product because it is at low levels relatively difficult to distinguish from background contamination, if you suppose some magic gamma capture.
But - to argue devil's advocate. If the reaction is hypothesised vanilla PF d+d->4He+gamma with other pathways suppressed and the gamma absorbed all is good for reaction products.
As far as interactions with adjacent charges go I can't see how that could work because strong and weak forces are very short-range so the only coupling available is electromagnetic - now we get to an area I do have more background in. The only interactions can be with local electric and magnetic field and therefore indirectly with far charges. That does not allow gammas (or gamma level energy) to be absorbed in any way I can see.
Electrostatic coupling is subject to speed of light and so the two main pathways will be much faster than electrostatic (or magnetostatic) coupling to any adjacent nucleus. So it is difficult to see that any such mechanism could suppress these.
It would be interesting to see proper people taking these hypotheses and joining the dots to find one that fits all the constraints. However if LENR does not exist, as seems most likely, that will never be possible because there is no workable hypothesis. the attempts I've seen ignore most of the constraints and propose something that would get round just one constraint.
Eric Walker wrote:Hi -- this is my first post to this forum. I found Tom Clarke's comments informed and interesting. You seem to know what you're talking about, and I'd like to get some additional details. By way of introduction, I have no background in nuclear physics, and anything in the field I refer to has been picked up on the side, and probably very inadequately.
The other side of this is that nuclear reactions, once they happen, have multiple paths all of which result in high energy released, and therefore high energy products. The energies here are MeV typically.
One question I have here has to do with the probabilities of the different pathways. My understanding is that these probabilities are partly a function of the time that is required for a given process to occur. Gamma emission takes a long time, so it is a rare branch in a d(d,*) reaction. Neutron, tritium and 3He emission take less time and so are much favored, relatively speaking. Is this understanding correct?
What are the possibilities for electrostatic coupling between a (hypothetical) short-lived [dd]* resonance and sources of charge in the immediate vicinity (loosely bound electrons, free protons, nucleons), such that the energy of the nuclear transition about to occur is kicked to these sources of charge instead of the usual branching to gamma emission or prompt particles? I understand that transfer of energy by way of electrostatic coupling is nearly instantaneous when it occurs. This suggests to me that if the process is at all possible, it would predominate, due to its rapidity.
As an engineer look at the improbabilities here:
(1) find some way round the Coulomb barrier. Seems impossible but many such things turn out to be possible, so let us suppose this can be done.
I assume that occasionally there will be an electric arc that will occur between electrically insulated grains in a metal that has a lot of impurities in it. I would guess that the power densities in such arcs are astronomical. Is this understanding mistaken?