QED & In-Ground Electrons: Why No Photon Emission?

[fxdung]

In ground state electron does not emit photon.Can we use QED to explain why in ground state electron does not emit any photons?

 

[phinds]

When it's in the ground state it isn't doing anything so why SHOULD it emit photons?

 

[fxdung]

Follow QED electrons would always be possible to emit photons even in ground state of atom. But in fact atom is stable.Thus why I ask the question.

 

[PeterDonis]

Follow QED electrons would always be possible to emit photons even in ground state of atom.

Why do you think this is true? Do you understand what "ground state" means?

 

[fxdung]

I would like use QED to demonstrate the existence of ground state.

 

[PeterDonis]

I would like use QED to demonstrate the existence of ground state.

That's a different question from the question of why an electron does not emit a photon when it is in the ground state. You can start a separate thread if you want to discuss that question. If you aren't convinced that a ground state exists, for an electron or anything else, then your question in the OP of this thread makes no sense and we can just close this thread.

 

[Dale]

Can we use QED to explain why in ground state electron does not emit any photons?

If it could emit a photon then it wouldn’t be the ground state, by definition. By the way, it is not the electron that emits the photon, it is the atom. And it is not the electron that is in the ground state, it is the atom.

 

[fxdung]

I think electron would emit photon because nucleus too heavy to motion to radiate(?)

 

[Dale]

I think electron would emit photon because nucleus too heavy to motion to radiate(?)

An electron cannot emit a photon, it would not be able to conserve both energy and momentum. It has to be the atom as a whole in order to conserve both. This is a fairly straightforward exercise to calculate for yourself. I recommend it.

 

[bhobba]

When it's in the ground state it isn't doing anything so why SHOULD it emit photons?

Your answer is a very common view of it, and indeed would likely get full marks in an introductory QM course, at least I would give it full marks, but a more advanced look at it shows what is going on is more subtle.

It will not emit a photon because its in the lowest state it can go. However it is still doing 'something' because it's not in a stationary state as its coupled to the Quantum EM field that permeates all of space which is why it can still absorb photons. If its not in the ground state, but an excited state, again while supposedly in a stationary state, it isn't really, but as previously mentioned coupled to the Quantum EM Field. Again the electron and EM field, as a system, will change with time, and it will eventually emit a photon, or perhaps even absorb another one.

Their seems to be a lot of queries along these lines at the moment, so I will start a new thread with the full answer and associated detail. Excellent introduction to why we need Quantum Field Theory as well.

Thanks
Bill