Electric-dipole selection rule
= Electric-dipole selection rule
= Dipole selection rule
{synonym}
Because the position operator has odd <parity>, an electric-dipole matrix element vanishes between states of the same parity. For orbital-angular-momentum eigenstates, the full rule is $\Delta\ell=\pm1$ and $\Delta m=0,\pm1$, with the field polarization selecting the allowed change in $m$.