- #1
lawlieto
- 15
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Consider a multi-electron atom. (In our course we deal with alkalis mostly so that we have energy levels which are similar to the hydrogenic ones with quantum defect. I don't know if that is relevant here)
Edit: l = orbital angular momentum of a single electron, L = total orbital angular momentum of the electrons, J = L+S with S = total spin
For an electric dipole transition in hydrogen Δl = ±1. Since we only consider one electron jumping at a time in multi electron atoms, for that single electron it's still true that Δl = ±1. However, one of the selection rules for multi electron atoms is that ΔJ=0,±1. Since ΔS=0, ΔL=0,±1. (if L=0 initially, then the 0 change is not possible). How is it possible for total angular momentum change to be 0 though? If only one electron transitions at a time and one photon is emitted, that photon carries away ±1 unit of angular momentum, but if the overall angular momentum change of the atom is 0, how is angular momentum conserved?
For instance, if an electron jumps from 4s->3p there is already +1 change in ΔL. This single electron cannot go 4s->3s so that ΔL=0, since that is forbidden for an electric dipole transition. So for a e.g. 4s->3p transition, do the other electrons rearrange themselves somehow? I was thinking the other electrons must have some role in this, as this 0 change in L is not possible for a single electron atom.
Edit: l = orbital angular momentum of a single electron, L = total orbital angular momentum of the electrons, J = L+S with S = total spin
For an electric dipole transition in hydrogen Δl = ±1. Since we only consider one electron jumping at a time in multi electron atoms, for that single electron it's still true that Δl = ±1. However, one of the selection rules for multi electron atoms is that ΔJ=0,±1. Since ΔS=0, ΔL=0,±1. (if L=0 initially, then the 0 change is not possible). How is it possible for total angular momentum change to be 0 though? If only one electron transitions at a time and one photon is emitted, that photon carries away ±1 unit of angular momentum, but if the overall angular momentum change of the atom is 0, how is angular momentum conserved?
For instance, if an electron jumps from 4s->3p there is already +1 change in ΔL. This single electron cannot go 4s->3s so that ΔL=0, since that is forbidden for an electric dipole transition. So for a e.g. 4s->3p transition, do the other electrons rearrange themselves somehow? I was thinking the other electrons must have some role in this, as this 0 change in L is not possible for a single electron atom.