I am wondering why a spin-S particle have only the term up to $k=2S$ in his multipole expansion ?
It seems that the Wigner-Eckart theorem shows the relation between spin and multipole expansion but I can't see why !
Thank you
I am wondering why a spin-S particle have only the term up to $k=2S$ in his multipole expansion ?
It seems that the Wigner-Eckart theorem shows the relation between spin and multipole expansion but I can't see why !
Thank you