# Gamma-ray decay Spin-rules

Pete137
Hi,

When i studied gamma-decay i encountered a set of transition rules telling for each radiation type (E1,M1,E2,M2,...) which transitions where allowed. For instance: a gamma ray emmited by E2 changes the parity and $I_{intial}=I_{final}+2$. Where you must know how to add angular momentum vectors in QM. I can apply this but don't they forget something? The gamma foton emitted carries an amount of intrinsic (spin) angular momentum of +1 or -1. Why is the foton spin not in the above formula?

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