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djclub2005
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Does anyone have a good understanding of why the spin selection rule (delta S = 0) holds for Russell-Saunders coupling in smaller atoms, but not for jj-coupling in larger atoms? For example, a transition from a triplet 2P to singlet 1S in helium is "disallowed," but a transition from a triplet 6P to singlet 6P in Hg is allowed. Some explanations say that photons do not directly affect spin, but what about radio waves flipping spin in NMR/ESR?
Also, does anyone know why you can't go from, say, triplet 3S to singlet 2S? It seems that a spin flip 1/2 -> -1/2 should account for a photon's angular momentum, so this would be allowed?
I appreciate any input.
Also, does anyone know why you can't go from, say, triplet 3S to singlet 2S? It seems that a spin flip 1/2 -> -1/2 should account for a photon's angular momentum, so this would be allowed?
I appreciate any input.