Photon and energy level

In summary, there is a finite probability for an electron to jump to the next energy level even if the energy of the photon does not exactly match the energy difference between the two levels. This can occur through assisted transitions, the uncertainty principle, and virtual energy levels. This is a result of the Heisenberg uncertainty principle and the finite lifetime of excited electronic states.
  • #1
bloupo
4
0
What if an electron at a certain energy level receive a little bit more energy from a photon than the difference between its current energy level and the next one, will it jump to it ?
I see written in textbooks that the photon energy must exactly match the difference between two energy level for the electron to jump from one to the other. So what ? let's say an electron with the difference btw its actual energy level and the next one of 12eV and a photon of 12,4 eV knock on his door , will he just ignore him bc is not exactly 12 or will it jump to the next one and keep some of this energy ??

Thanks
 
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  • #2
The electron must have exactly 12 eV of energy to jump to the next energy level. However, I'm not sure if the extra 0.4 eV can be absorbed by the whole atom/molecule in some way. Perhaps this can only occur in molecules or bulk materials since they have far more degrees of freedom and energy levels?
 
  • #3
thank yo, so the electron will actually jump from one energy level to the other(considering the 12eV difference in energy levels) if it encounters a photon of 12,4 eV right ??
 
  • #4
No, there is no guarantee. If there is nowhere for the extra energy to go, then it will not jump.
 
  • #5
Some of the extra energy can go into exciting translational degrees of freedom of the atom, i.e. the atom also has some kinetic energy after the transition. This probably tends to be washed away to some extent by the Doppler broadening of the spectral lines, which is due to the motion of the atoms before the transition, and is probably a larger effect.
 
  • #6
Well, first off, nothing is perfectly monocromatic (or mono energetic), there's a built-in uncertainty in both the source and the electron, and if the width if those distributions overlap then there is still a non-zero probability that the transition occurs. This probability simply rises the closer to resonance you get.

Secondly, an assisted transition can occur, as was mentioned above, and this is when the energy difference is made up for by something else. In gases this is often doppler shifts from atoms increasing or decreasing their speed as a result of the interaction and in solids it is often phonons that can get absorbed or deposited in the process to conserve energy.

Thirdly, even if the energy does not match up in the end, the "transition" can still occur during a sufficiently short time intervall, before the wavefuntion has canceled due to destructive interference. This is usually not referred to as a real transition, but as a "virtual energy level", and this feature is significant in for examlpe two-photon raman transitions which can occur also far off-resonantly.
 
  • #7
Zarqon said:
Well, first off, nothing is perfectly monocromatic (or mono energetic), there's a built-in uncertainty in both the source and the electron, and if the width if those distributions overlap then there is still a non-zero probability that the transition occurs. This probability simply rises the closer to resonance you get.

Interesting. I was not aware that this could occur. Any chance you could elaborate a bit?
 
  • #8
Drakkith said:
Interesting. I was not aware that this could occur. Any chance you could elaborate a bit?

Considering an atom, this is simply an expression of the Heisenberg uncertainty principle. Apart from the ground state, all electronic states have a finite lifetime, as an excited electron will eventually decay. This finiteness of ##\Delta t## means that there is an uncertainty ##\Delta E > 0## on the exact energy of the excited state. We say that the state has a certain width in energy, which is inversely proportional to its lifetime.
 
  • #9
DrClaude said:
Considering an atom, this is simply an expression of the Heisenberg uncertainty principle. Apart from the ground state, all electronic states have a finite lifetime, as an excited electron will eventually decay. This finiteness of ##\Delta t## means that there is an uncertainty ##\Delta E > 0## on the exact energy of the excited state. We say that the state has a certain width in energy, which is inversely proportional to its lifetime.

That's crazy! I love QM!
 

1. What is a photon?

A photon is a basic unit of light or electromagnetic radiation. It is a particle that has no mass but carries a specific amount of energy. Photons travel at the speed of light and can behave like either a wave or a particle.

2. What is an energy level?

An energy level, also known as an energy state, is a specific amount of energy that an electron can possess within an atom. Electrons can only exist at certain energy levels, and they can move between levels by absorbing or emitting photons.

3. How are photons and energy levels related?

Photons and energy levels are related because photons are the particles that carry energy, and energy levels are the specific levels at which an electron can absorb or emit energy in the form of photons. The energy level of an electron determines the energy of the photon it emits or absorbs.

4. What is the relationship between energy level and electron configuration?

The energy level of an electron determines its position in the electron configuration of an atom. The number of electrons in each energy level determines the overall electron configuration and the properties of the atom, such as its reactivity and chemical properties.

5. How do changes in energy levels affect the behavior of atoms?

Changes in energy levels can affect the behavior of atoms in various ways. For example, when an electron moves to a higher energy level, the atom becomes more reactive and may form chemical bonds with other atoms. On the other hand, when an electron moves to a lower energy level, the atom becomes less reactive and may release energy in the form of light or heat.

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