Hey, I'm just reading through from AP notes and was slightly confused about selection rules. It's my understanding that change in the spin angular momentum is forbidden in electron transitions dude to the LS coupling limit. However, when reviewing Hund's rules and looking at the possibilities for the first excited state, it seems that the spin quantum number can either be 0 or 1. Could someone please clear up my misunderstanding about the restrictions on the spin in electron transitions? Thanks.