I was just reading the Wikipedia article on U-233 and it noted that U-233 often contains U-232 which makes the material difficult to handle because the decay chain of 232 contains strong gamma emitters. It then lists the decay chain, but all the elements listed are alpha or beta decays. What gives?
Thanks,
Rob
In an alpha decay, the nucleus gives off two protons and two neutrons reducing its atomic number by 2 and its atomic mass by 4. In a beta decay a nucleus gives off an electron converting a neutron to a proton increasing it’s atomic number by 1 and leaving its atomic mass unchanged (or gives off a positron converting a proton to a neutron).
In either case photons are also given off to balance the energy (conservation of mass-energy). Something that is a strong gamma emitter is giving off very energetic photons, but all alpha and beta decay gives off some photons (I believe).
*All * nuclear decay processes emit gammas. That’s where the released energy goes. How energetic the gammas are depends on the rate of decay, the relevant nuclear energy levels, et cetera. So whether a decay step emits nasty gammas or not has little to do with whether it’s an alpha or beta decay (or something rarer, like fission or K capture).
I thought the released energy was wrapped up in the emitted particle.
Most of what we think of as radioactive decays are from one isotope to a different isotope. These usually emit either alpha or beta particles, and do not involve gamma rays (though you might get some secondarily from the emitted particle interacting with other atoms). The energy released is all in the emitted alpha or beta particle (well, strictly speaking, mostly in the emitted particle, and some in the recoiling nucleus).
However, some radioactive decays are from an excited state of an isotope to the ground state of the same isotope. These decays can’t emit alpha or beta particles, since either of those would change the isotope. The only option left is photons, which will be very high energy, i.e., gamma rays.
WHAT?
The overall process is FISSION and the problem is, what decay products (of U232) emit 2.6 mega-electron volt gamma radiation ?
One specific child of U232 is Thallium 208 … which undoes beta decay to Lead 208.
Thallium 208 is 207.9820187(21) AMU
Lead 208 is 207.9766521 AMU
(An amu is 1.66E-27kg )
Yes, that is quite a weight loss, via beta decay… With no massive particle to take the energy away, it is observed the energy is released as 2.8 MeV gamma rays.
Not if by “a different isotope” you mean one of the same element. Alpha or beta decay both change the proton count of the nucleus, giving you a different element.
As other folks have noted, gammas are usual emitted in concert with alphas & betas: a parent nuclide emits an alpha or beta and changes into a daughter nuclide, but the daughter is in an excited state (akin to how an electron can be in an excited state in an atom.) It then emits the extra energy as a very high-energy photon.
If you’re curious about which specific decays in the U-232 decay chain are the gamma emitters, I found this figure from an MIT Open Course that shows the gamma emitters as well. Short answer: almost all of them emit gammas along with the alphas & betas.
True, you’d only get the same element through neutron emission, which is a rather rare form of decay (though I’m pretty sure it still happens occasionally).
And I’m not aware of any case where gammas actually accompany alphas or betas. The alpha or beta decay to an excited state and the subsequent decay of that excited state via gammas are two different processes, albeit often the gamma decay is very quick after the alpha or beta decay.
A good example would be to look at the decay chain of Cs137
Cs137 is normally used as a gamma ray source. However Cs-137 decays purely by beta emission. It either goes from Cs137 to Ba137 emitting a 1.174MeV beta particle about 5% of the time.
The remaining 95% of the time it decays to Ba-137m emitting only a 512kEv beta particle.
Ba-137m is a metastable isotope with a half life of about two and half minutes. It then decays to Ba137 emitting the characteristic 661.7kev gamma ray.
So we often say Cs137 emits 661.7 kev gamma ray ( and that’s what you look for in spectroscopy to detect Cs-137 you look for that energy gamma ray) even though it doesn’t. However the 1/2 life is so much less for the metastable state compared to the parent nuclei, for all intents and purposes it does emit a gamma ray when it decays, even if the actual decay mechanism is pure beta.
The same holds true for a lot of decays, we may say the decay emits a gamma but the actual decay is only alpha or beta
Cobalt 60 has a few decay paths
So the actual decay mechanism from one isotope to another is either by alpha or beta ( other options but lets keep it simple) , the isotope it dacays to may have excess energy and dumps that energy in the form of a photon as is settles down to a less energetic state.