where | S ⟩ ⟩ is an S -state, non-degenerate, wavefunction, which is symmetric or antisymmetric under inversion: I | S ⟩ ⟩ = ± ± | S ⟩ ⟩ . Since the product of the wavefunction (in the ket) and its complex conjugate (in the bra) is always symmetric under inversion and its inverse,