Why does some reactions do't go to the fundamental state?

[Frank Einstein]

Hi everybody, after studyng a little bit of nuclear physics I have noticed that many reactions (α,β,γ...) end with the new particles in excited states which rea¡main in those for a little time before going to the fundamental.

I don't know why this happens instead of going directly to the fundamental state.

Can someone please tell me why this happens?

Thank you very much.

 

[mfb]

Usually, both reactions are possible. The more likely one depends on things like spin, transition energy and sometimes a few other factors. Why would you expect some transitions to be impossible?