Scattering Amplitude for an Atom

Next integrating with respect to cp results in 2ti. Now we should integrate (5.16) with respect to r and find the angle (or q-) dependence of the field intensity scattered by an atom 

We see that the scattering amplitude depends only on the modulus of q and is spherically symmetric in the -space. Since pa(r) is unknown there is no universal formula for each atom but we can analyze two asymptotic cases  

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