So I was reading about Fermi surfaces. One of the first things that is obvious is that energy excitations happen at the boundary of the surface as the electrons deeper inside the surface do not have room to'grow' as higher states are occupied and those will have to emptied first.
Lets say there is a state at a higher energy level than the Fermi energy, if energy input is exactly the difference between that energy level and that of the electron deep inside the surface would that electron make the transition? If the electron progress in energy levels directly then it makes sense to me that it should. But apparently it cannot. Unless I have something confused.