# Feynman diagram for radiative transition

by kuecken
 P: 16 Hi, I was just trying to draw a Feynman diagram for ψ' to $χ_{c}$ states. So we have a electromagnetic transition. I feel tempted to just have c and $\bar{c}$ coming in and letting a γ leave from one of the legs. But that looks like an incomplete Feynman diagram to me. Maybe I have to get two photons out? Can someone help me with this please!