Beta emissions and quarks, really?

Up becomes down and out comes a positron

All atomic nuclei are made up of different numbers of protons and neutrons, the different combinations of protons and neutrons give us the elements and their isotopes.

Radioactivity is the emission of particles from the nuclei of atoms.


Of all the different types of radiation, I think my favourite is probably beta emission and it is this I am going to talk about in this post.


Beta emission is where an electron, or a positron, is ejected from the nucleus of an atom. Now for those of you paying attention, I am sure you have just raised an eye brow and thought, "hold on a minute, you said that the nucleus is made up of protons and neutrons, no mention of electrons there!" and this is absolutely true. There are NO electrons in the nucleus of an atom. None whatsoever and yet, they can still be ejected from the nucleus!

I think this is absolutely fantastic.

Many believe that we can view a neutron as a proton and an electron bound together. By that logic, positron emission, the emission of a positively charge electron, implies that a proton is a positron and a neutron bound together. This is not right.

The current thinking is that protons and neutrons are actually made up of quarks. This is part of the Standard Model, which appears to have had a rather spectacular result recently with the discovery of the Higg's boson.

Quarks can change and as a result of this change electrons or positrons can be produced that come whizzing out of the atomic nucleus.

Take Fluorine 18, this has 9 protons and 9 neutrons. The stable form of fluorine is fluorine 19, 9 protons and 10 neutrons. The extra 1 neutron in fluorine 19 makes it a happy bunny. But fluorine 18, completely unhappy and it shows this by kicking out a positron, like so

¹⁸F -> ¹⁸O + e⁺

one of the protons has changed to a neutron, so only 8 protons remain, and the 9 neutrons become 10, making it an Oxygen atom. Oxygen 18 is also a happy bunny and does not decay any further.

So, this is the thing that I am going to be pondering for the next week or two, Fluorine 19 - happy, Fluorine 18 - unhappy, Oxygen 18 happy. One neutron difference between F19 and F18 is enough to make the second, F18 unstable. It seems that the neutron has a calming effect. Will ponder this in a later post.

Now, to finish, fluorine had 9 protons and 9 electrons to balance it out. Oxygen, the final product, only has 8 protons so only needs 8 electrons to balance it out and make it electrically neutral. So what happened to that extra electron?

Well, maybe, the positron, which is the anti particle of the electron, interacts with the extra electron to form something that we could call positronium. The two particles could then annihilate each other and decay into gamma rays.

Now that would be really cool.