# Can an electron collide with the nucleus of an atom?

1. Aug 19, 2011

### ItsDaveDude

Can an electron (from outside the atom) collide with the nucleus of an atom, and does this happen at normal energy levels? What usually happens when it does?

If it doesn't happen is it because the electrons of the atom repel the incoming electron with their charge.

Finally same question, but this time its a photon colliding with the nucleus, does this change anything, and what is the result and why?

Thanks!

2. Aug 20, 2011

### K^2

The S-shell actually has non-zero expectation value at the nucleus. It all depends on what you call a collision.

3. Aug 20, 2011

### ItsDaveDude

I don't know how to refine my concept of collision to ask the question better.

Can you sub-divide the answer to my question into the different ways you would define collision so I can understand better and have an answer to the questions I asked based on how the answer changes (and why) according to your definitions of collision.

4. Aug 20, 2011

### K^2

Basically, if your question is whether you could find an electron within the nucleus at any given time, the answer is yes, provided that the electron in question is in s or s-hybrid orbital. At any given time, there is a small chance that this electron would be found in the nucleus.

However, this does not really result in any special kind of interaction. Electron is a wave, and so are the particles making up the nucleus. They already interact electromagnetically. That's what keeps the electron where it is. And the electron does not interact strongly, so it being within the nucleus doesn't change anything compared to when it's in the vicinity of the nucleus.

5. Aug 20, 2011

### ItsDaveDude

Ok, so according to your logic, an electron from outside the atom could not collide with any part of the nucleus (because it is not in an s or s-hybrid orbital). Is that because the other electrons would repel it?

What about the case of a photon?

As an aside, I've been told by Feynman that photons are particles, and that their wave behavior is explained by probability amplitude calculations and that they aren't really waves. I don't want to open a can of worms about whether they are or not, but can you tell me so I know is Feynman generally regarded as wrong then on this, and what is the general state of the art on this idea (again I don't want to know if they are waves or particles, but what is the current consensus belief today (as opposed to Feynman's time) if there is one).

6. Aug 20, 2011

### K^2

I just realized you said "from outside", so let me refine everything.

First of all, even an external electron can be represented in term of spherical waves, so it can still be written in terms of orbital hybrids. If the resulting hybridization includes s-shells, then there is a probability that the electron will be found within nucleus. If that is what you mean by collision, there you go.

For an external electron, you can also look at momentum transfer. That's the scattering event. At low energy, an incoming electron will scatter from the electrons around the atom, rather than nucleus. At high energy, you can get electron to scatter from the nucleus itself. Same deal with the photon. So if that's what you consider collision, then it's a matter of energy.

I think you misunderstood Feynman on particle-wave duality.

7. Aug 20, 2011

### ItsDaveDude

You don't have to take my interpretation of Feynman, listen to him state it directly here within the first 30 seconds and explain why:

And my question still is: I've been told by Feynman that photons are particles, and that their wave behavior is explained by probability amplitude calculations and that they aren't really waves. I don't want to open a can of worms about whether they are or not, but can you tell me so I know is Feynman generally regarded as wrong then on this, and what is the general state of the art on this idea (again I don't want to know if they are waves or particles, but what is the current consensus belief today (as opposed to Feynman's time) if there is one).

8. Aug 20, 2011

### K^2

Anything Feynman says about QED is right. That's the shortest answer I can give you to your question. But you are still misunderstanding the distinction between particle and a wave if such a question comes up.

9. Aug 20, 2011

I dont know if "electron/K" capture is relevant to this discussion.Although the effect refers to orbital electrons,at previous times those electrons could have been outside the atom the total event going through different stages.

Last edited: Aug 20, 2011
10. Aug 20, 2011

### ZealScience

What about electron capture of protons? Do you consider it as an example of collision?

11. Aug 20, 2011

### K^2

That's not any different from coulomb scattering. Electron just happens to emit W boson instead of a photon and you get a flavor/isospin change.