Classical Description of Molecules in Time-Dependent Fields

The stationary-state perturbation theory used in this section is applicable only to nondegenerate states degenerate perturbation theory must 

3 CLASSICAL DESCRIPTION OF MOLECULES IN TIME-DEPENDENT FIELDS 

In the classical electromagnetic theory of light, light in vacuum consists of transverse electromagnetic waves that obey Maxwell s equations [1,2] 

It is easy to show from Maxwell s equations that Eq k = B k = 0 (i.e., both fields point normal to the direction fc of propagation as required in a transverse electromagnetic wave), that Eo Bo = 0, and that Eqs. 1.38 describe linearly polarized light with its electric polarization parallel to Eo as shown in Fig. 1.5. 

This automatically satisfies V B = 0 in consequence of the vector identity 

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