What is the difference between Photofission and Photodisintegration?
Posted May 24, 2021, 9:32 AM UTC
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Posted May 24, 2021, 9:32 AM UTC
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Photofission is fission induced by a photon, and photodisintegration is just any time a photon knocks a particle (like a proton, neutron, alpha particle) out of a nucleus.
So would this make photofission a form of photodisintigration?
Sure, you could say that.
Where is the line drawn from one to the other? Anything bigger than an alpha particle?
For that matter, can you knock off varying size chunks from a nucleus or do they generally just split into mostly equal products?
There isn't a sharp line, but for most practical purposes, it either looks like something heavy splitting roughly in half (fission), or just something spitting out one or two light particles (photodisintegration).
In-between cases are possible, but rare in practice.
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Ok, cool. I’m only a bit more knowledgeable than the average person when it comes to this sort of stuff, I mostly study fusion-related stuff in my free time. Thanks!
Wouldn't it be the other way around?
Fissioning a nucleus to produce a hydrogen nucleus instead of a strontium nucleus is still fission right? Or are we talking something like beta decay?
Yes, it is still fission, but if it was photofission, as in fission induced by a photon, it is also photodisintigration.
So in photodisintegration you cannot get a particle larger than alphas?
You can, but it's relatively rare.
Can something lighter than an alpha particle like deuterium or helium-3 be knocked out of a nucleus by a photon?
Yes, a deuteron, triton or 3He nucleus could all be emitted, assuming the incident gamma ray has enough energy to overcome the binding energy for removing the outgoing particle.
You can also emit multiple particles, such as 2 or 3 neutrons, or a neutron and a proton, etc.
If it's not forbidden by a conservation law it's possible. In this case nothing is forbidden if your photon energy is sufficient. But allowed processes can still be really rare. Alpha particles are tightly bound, if more than isolated protons or neutrons are emitted it's usually an alpha particle.
If it's too large we would call it fission. Doesn't really matter. If there is any ambiguity an author should specify what they mean.
You can and in fact there are even rare spontaneous fissions that give two large nuclei plus a third light nucleus. Must often an alpha, but sometimes others either lighter like He-3 or heavier like lithium.
Do you have any good book recommendations for nuclear physics for moderates (I've taken up to E&M physics in uni)? I've never even heard oh photofission until this point, and I didn't even know it was possible.
Photofission isn't something that's talked about too often, so it's not surprising that you haven't heard of it. But I'd recommend Introductory Nuclear Physics by K. Krane. It's the standard undergrad nuclear physics book, giving a pretty good survey of the field. It's a little old, so it doesn't cover what's going on at the cutting edge, but that usually isn't covered in a first course anyway.
Thank you very much, adding to my Amazon cart!
Another great book is Loveland, Morrissey, and Seaborg's Modern Nuclear Chemistry. LMS is a fantastic readable text on nuclear science, and is also a useful reference text. It also just got updated in the last five years.
Second Krane. Good book.
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Would you have to have a high energy photon to make this happen? Like a gamma ray or X-ray?
Yes, generally gamma rays.