MrJammin

A moving charge radiates Electromagnetic waves, so if a electron were to be accelerated to a velocity, and under the conditions that no forces were exerted on the electron, the electron would eventually come to a rest after radiating EM waves right?

Papabravo

That would be the view of classical mechanics, but electrons march to a slightly different tune. I'll leave it to you to find out why they can't loose all their energy and come completely to rest. The truth is actually stranger than fiction.

MrJammin

I take it your talking about the uncertainty principle? That if we can't know the position and momentum of the electron specifically. But, considering how small h-bar/2 is, the electron will come fairly close to radiating all of its energy correct?

Papabravo

No that's not where it is at. Bound electrons have a minimum energy called the ground state. In this state they have no more energy to give up and therefore cannot radiate. The norm of the wave function (psi*psi) gives the probability of finding an electron of a given energy at some distance from a nucleus. It is because there is a minimum quantized energy state that an electron cannot come to rest.

MrJammin

Right, but I wasn't talking about a bound electron. I mentioned that the electron had no forces acting upon it, it is a free electron moving in space.

Papabravo

OK, so what do you suppose is the mean free path of such an electron?

For fermions, which must obey the Pauli exclusion principle, there is no state of zero energy. The lowest energy of a free fermion is called the ground state energy. Since there are no forces on the particle it cannot be contained or localized in a region of space and it will interact eventually. Still there is a minimum energy below which the fermion cannot go. If you can't reduce the energy you can't reducde the momentum and you can't bring the particle to rest with no potential function.

MrJammin

Ah, I see what you were talking about now. Thanks.