Subject: questions about electrons and photons

When an electron bound to an atom absorbs or loses energy, it moves to a higher 
or lower energy level. Is this movement between energy levels instantaneous or 
does it take a finite amount of time to complete the transfer ? My understanding 
is that electrons can only exist in discrete energy levels and not inbetween 
levels. So what happens to the electron at the moment of energy gain ? Does it 
simply vanish from the energy level it occupied and immediately re-appear in 
another energy level or does it take a finite amount of time to make the 
transfer ?

When an electron in atomic orbit absorbs (gains) energy from a photon, how does 
the electron physically utilize this additional energy. Obviously the electron 
is a fundamental particle and will not change mass,charge,spin, etc ... so what 
REALY does change from the electrons point of view ? I'm not referring to an 
energy level change which is the result of energy gain or loss ... I'm more 
interested in the physical processes that occur to the electron which eventually 
result in a level change.

Is the exact mechanism understood by which a photon is created when an electron 
drops to a lower energy level ? How is the required exact energy extracted from 
the electron ? What mechanism extracts the energy from the electron and what 
mechanism creates the photon ? When is the photon created - before the electron 
leaves the original level - whilst the electron is between levels - or when the 
electron appears in the new energy level? How long does it take to create the 
photon - is it instantaneous or does it take a finite time ? Does the photon 
appear "complete" or does it have to be constructed, so to speak. How close is 
the photon to the electron when it's created ? 

Re: questions about electrons and photons