Question

Explain why atomic scattering power decreases with angle

Answer 1

The measure of scattering power if an individual atom is defined as the atomic scattering factor.Each element has different atomic scattering factor,which represents how strongly x-ray interacts with those atoms.

Now, the incoming X-rays are scattered by the electrons(electron cloud) of the atoms. As the wavelength of the X-rays (1.5 to 0.5 A) is of the order of the atom diameter, most of the scattering is in the forward direction. For neutrons of the same wavelength the scattering factor is not angle dependent due to the fact that the atomic nucleus is magnitudes smaller than the electron cloud. It is also obvious that the X-ray scattering power will depend on the number of electrons in the particular atom. The scattering power of an atom 'decreases' with increasing scattering angle and is higher for heavier atoms.