The angular eigenfunctions of atoms can generally be represented by eigenfunctions of the orbital angular mo- mentum operator, i.e. the spherical harmonic eigenfunctions Yl,m. (c) Prove that the electric dipole transition can only happen between initial and final states of opposite parity? What is then the selection rule for l? (d) Why do so called forbidden transitions occur that violate the above mentioned selection rule? What is the characteristic property of such transitions?

The angular eigenfunctions of atoms can generally be represented by eigenfunctions of the orbital angular mo- mentum operator, i.e. the spherical harmonic eigenfunctions Yl,m. (c) Prove that the electric dipole transition can only happen between initial and final states of opposite parity? What is then the selection rule for l? (d) Why do so called forbidden transitions occur that violate the above mentioned selection rule? What is the characteristic property of such transitions?