We see from these two equations that in order to have non-zero Δ Δ ε ε , the electric and magnetic dipole moment operators ( M ^ ^ ( e l e c . d i p o l e ) and M ^ ^ ( m a g . d i p o l e ) ) must transform as the same irreducible representation. C n and D n are the only point groups where this can occur, making only chiral molecules CD active.