Excitation to higher energy levels

In summary, there is a rule known as the parity selection rule which states that the 2s level of hydrogen cannot decay to the 1s level. Instead, it decays by two-photon decay, which results in a continuous spectrum of photons with energies equal to the difference between the 2s and 1s levels. This is a significant factor in the UV and optical continuum observed from many nebulae.
  • #1
Chemist@
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If an electron gets excited from K to L shell, it will actually finish in the 2p subshell and then deexcite to 2s and 1s at the end, right?
 
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  • #2
It 'can' de-excite from 2p-2s or it 'can' directly de-excite to 1s. Same applies to excitation.
 
  • #3
But that doesn't seem to follow the selection rules.
 
  • #4
Which rules are you talking about?
 
  • #6
Anyone?
 
  • #7
Not sure what the question is, if there is one. :smile:

Are you maybe asking, "If an atom decays from 2p to 2s, then how does the 2s subsequently decay to 1s, since this violates the rule for allowed transitions?"

From http://www.tapir.caltech.edu/~chirata/ay102/Atomic.pdf:

One notable feature of the above is that the 2s level of hydrogen cannot decay: the only lower energy level is 1s, and the parity selection rule forbids this. The 2s level instead decays by two-­photon decay: H(2s) → H(1s) + γ + γ. The sum of the energies of the two emitted photons is E2s−E1s = 10.2 eV. The photons have a continuous spectrum since there is no other constraint on their energies. This is a major contributor to the UV/optical continuum from many nebulae.
 
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  • #8
Great. Thanks.
 

Related to Excitation to higher energy levels

1. What is excitation to higher energy levels?

Excitation to higher energy levels refers to the process of an atom or molecule absorbing energy, typically in the form of photons, and transitioning to a higher energy state. This can occur through various mechanisms such as collisions with other particles or absorption of light.

2. Why do atoms and molecules get excited to higher energy levels?

Atoms and molecules get excited to higher energy levels in order to reach a more stable state. The electrons in an atom are arranged in specific energy levels, and when they absorb energy, they can move to a higher energy level. This allows the atom to achieve a more stable electron configuration, reducing its overall energy.

3. What happens to an atom or molecule after it has been excited to a higher energy level?

After an atom or molecule has been excited to a higher energy level, it will eventually return to its ground state. This can occur through the emission of photons, where the excess energy is released, or through collisions with other particles, which can transfer the excess energy to them.

4. How does excitation to higher energy levels relate to spectroscopy?

Excitation to higher energy levels is a key aspect of spectroscopy, which is the study of the interaction between matter and electromagnetic radiation. By measuring the energy levels that atoms and molecules can be excited to, scientists can gather information about their chemical composition and properties.

5. Can excitation to higher energy levels occur in living organisms?

Yes, excitation to higher energy levels can occur in living organisms. In fact, many biological processes, such as photosynthesis, rely on the excitation of molecules to higher energy levels in order to function. Additionally, medical imaging techniques such as MRI also utilize excitation of atoms in the body to higher energy levels for imaging purposes.

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