Focusing and Deposition

The second term in Eqs. (12.55) can be rewritten as the product of a dynanijc polarizability tensor of the molecule, given as 

That is, the field-dependent component A W(X, t) of the LIP felt by the system)] given by 

This contribution may be viewed classically as being due to the interactioit df induced dipole, dmd(t) = (co ) % ,(f) created by the field, with the field that crearf it, with the energy of interaction being given by A W(X, t) = —z fye dmd. 

The only nonclassical aspect of the far off-resonance limit result, Eq, (12 is the dependence of the dynamic polarizability [Eq. (12.56)] on the flu coordinates X. This dependence is in accord with qualitative classical exp since we expect different molecular configurations to be more easily polarizabji others. However, it is only quantum mechanics, via Eq. (12.56), that advises compute this shape-dependent polarizability. 

To better understand these effects, we consider an atom interacting with a stand- ing-wave field of the form 

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