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Feb15-12, 05:04 AM
P: 1,863

I am reading about transition in Helium, and I have come across a question. It is clear that triplet-singlet transition are not allowed, i.e. ΔS=0. But in my book (Foot's Atomic Physics) it says that Δl = 1. This is what I don't understand. The selection rule Δl = 1 we derived for Hydrogen, where there was no electrostatic interaction and only a single electron making the transition. In Helium we *do* have an electrostatic interaction and two electrons -- then how can we reuse Δl = 1 again?

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