Selection rules for electric dipole transitions

There are, however, certain selection rules for electric dipole transitions which considerably reduce the number of possible transitions. They are extensively discussed and proved in reference and for diatomic molecules consist essentially of the following three rules ... 

Step 4. For a vibrational mode to be infrared (IR) active, it must bring about a change in the molecule s dipole moment. Since the symmetry species of the dipole moment s components are the same as rx, ry, and 1, a normal mode having the same symmetry as Ix, Ey, or 1 will be infrared active. The argument employed here is very similar to that used in the derivation of the selection rules for electric dipole transitions (Section 7.1.3). So, of the six vibrations of NH3, all are infrared active, and they comprise four normal modes with distinct fundamental frequencies. 

It follows that the selection rule for electric-dipole transitions [cf. Eq (4.70)] in a harmonic oscillator is An = 1. 

Selection rules for electric dipole transitions in terms of e/f levels, the rules are... 

In the present example neither x, y, or s lie on symmetry axes so that the same result is obtained for each. It is of great importance to note that the two vectors P Au) and P(Bu) arc at 90° to one another that P(.4 ) points along the b axis and that P B ) is a vector pointing somewhere in the ac plane. This a mast significant result for it enables us to develop selection rules for electric dipole transitions in crystals. The electric dipole transition moment between two factor group states X and w is... 

The most general selection rule for electric-dipole transitions, the type of transition that is relevant to almost all of the bands observed in the electronic spectra of transition metal complexes, is a group theoretical statement of the excitation process described in qualitative terms in Section 8.1. It is the following ... 

Once the rotational energies are computed, the rotational spectrum is obtained from the selection rules for electric dipole transitions ... 

SELECTION RULES FOR ELECTRIC DIPOLE TRANSITIONS to the applied field. 

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