Yes they are. They are transitioning through levels in the conduction band where you have plenty of them.

Every time you see a macroscopic phenomena, you are looking at a stupidly high amount of quantum levels with very similar energies.

That's a good point, I don't know what's up with that. Google just says, "A single oscillating electron does not continuously emit radio waves; it has a microscopic probability of emitting a single RF photon during a given cycle." It would be necessary to delve into the whole QED thing to get a better explanation, based on what I'm reading.

Either way, quarks don't have an electron-like magnetic moment, so they aren't capable of coupling to the EM field.