Excitation to higher energy levels

[Chemist@]

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?

 

[Adithyan]

It 'can' de-excite from 2p-2s or it 'can' directly de-excite to 1s. Same applies to excitation.

 

[Chemist@]

But that doesn't seem to follow the selection rules.

 

[Adithyan]

Which rules are you talking about?

 

[Chemist@]

It's at the bottom http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/hydazi.html.

 

[Chemist@]

Anyone?

 

[Bill_K]

Not sure what the question is, if there is one.

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 E_2s−E_1s = 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.

 

[Chemist@]

Great. Thanks.