Re: How long lasts the jump of electron from one energy level to another?

According to the Heisenberg uncertainty principle, one cannot say exactly 
where the electron is, nor exactly how long it will take to get there, nor 
how long it will stay there. It is possible that an electron at the 
beginning energy level disappears and an electron at the ending energy 
level appears. (This does not violate any law of physics if it occurs in a 
time that is less than that predicted by the Heisenberg Uncertainty 
Principle) Your question is good because it DOES take a finite amount of 
time for the energy transition to take place. Because of the finite time 
required for the transition, no spectral line can be truly monochromatic. 
For a gas, the shape and width of a spectral line is related to the time 
for the electron transition, the Doppler effect and the temperature and 
pressure of the gas. An expression for the spectral line of a gas that 
only takes into account the time of the electron transition is called a 
Lorentz Line. It is possible to develop a theoretical expression for the 
Lorentz Line, or the spectral line can be analyzed experimentally. In 
theory, the electron transition is instantaneous, but in reality, the 
width of the Lorentz Line shows that it does take some finite amount of 
time for the transition.