Ok so this a purely whimsical exercise on my part, but I am curious, can anyone imagine if such a thing as a catalyst for a nuclear process could exist, under any physical conditions? Presumably the answer is no, but I am curious as to why. Chemical reactions can of course be catalysed by interesting molecular structures, so I wonder if in principle an analogous nuclear structure could exist. I suppose the first thing is understand if an analogue to a covalent bond could be formed between nuclei. I suppose no, that the strong nuclear force just doesn't allow the formation of mutant joint nuclear structures to exist (either the parent nuclei fuse together into a larger roughly spherical structure or they otherwise rearrange themselves into a number of smaller roughly spherical structures); I know at least that no such thing has ever been observed. But I am not sure what properties of the strong nuclear force forbid this. Except that it is too strong I guess. I'm not sure what I am thinking of exactly, maybe that two nuclei share some valence nucleons or something. Maybe if your nucleus is really huge and the valence nucleons relatively loosely bound. Admittedly my knowledge of exactly how a covalent bond is stabilised is pretty sketchy, so maybe someone can explain that to me first. I of course get that somehow the sharing of electrons between the atoms lowers the energy of the configuration, but I am not sure why. Probably someone told me once but I can't remember. Also I suppose the nuclear force really just grabs nuclei and sucks them together; unlike covalent bonds where the attractive force due to the electron sharing is balanced by the coulomb repulsion of the nuclei. I suppose that is all there is to it. And I suppose the shell structure of nucleons is a lot more fluid than electronic shell structures. Perhaps if the inner shell nucleons had a much more stable structure than the valence nucleons though, so that the valence nucleons kind of just bounced around on the outside of the nucleus...
The answer is quite simple, really. It's because you're thinking in terms of chemistry, not nuclear physics. There is no comparison between the two; no such things as covalent bonds in atomics nor is there any such thing at all as "valence nucleons." Plainly put, your talking apples and oranges.
Covalent bonds, sure. But that is with known nuclei and ordinary physical conditions. If super-heavy nuclei are found to exist it could be a different story. Ok so they probably won't be even a little bit stable, but they might be. As for valence nucleons, those certainly exist, at least in the shell model: http://en.wikipedia.org/wiki/Nuclear_structure#The_shell_model Really there are lots of analogues.
I'll buy that, thanks. Please Register or Log in to view the hidden image! And the reason I wasn't aware of the nucleons is that I've never studied QM. I do understand that there are analogs, however they aren't very strong ones and apparently operate under totally different rules. Much as I said - apples and oranges.
not sure about fusion but the "catalyst" for fission is mass. naturally occurring uranium will fission spontaneously, enough mass will allow the fission to sustain itself.
kurros The answer to your question is a most definite _yes_. Do a google for "muon catalyzed fusion". For fusion, I believe there are also reactions that can be catalyzed by various trace isotopes that take part in the reaction but are regenerated by a final stage of the reaction. Usually by alpha emission, iirc. Interstellar hydrogen and (bismuth?) in a Bussard ram comes to mind.
Well, that's stretching the definition of catalyst quite a lot I'd say. Some kind of external agent would be nice. And ok sure, you can stick the whole thing in a sphere of beryllium to reflect neutrons back in on the stuff to increase the rate of reaction also. I guess I am thinking along different lines to this kind of intervention. Wow, I can't believe I had never heard of muon catalysed fusion before. That is extremely cool. I hope their research goes well.
Well, it's been know since about the 1950's or there abouts and pretty much gone nowhere, but you never know. I remember reading a bit by one of the original researchers, the went something like... 'there was a half an hour or so that we thought we had solved the energy needs of the human race... then we started calculating the number of fusions we could expect per muon and... oh well.' It is a pretty cool phenomenon though.
