I know that B(E1) spectrum can be obtained by using virtual photon method, experimentally. But how do you get it through any theory approach? Is there any code to do that?
you can calculat the B(E1) by using interacting boson model with s(L=0) d(L=2 and f (L=3) bosons. In the simple version IBM-1,one can get the negative and positive energy levels