Atomic form factor
In physics, the atomic form factor, or atomic scattering factor, is a measure of the scattering amplitude of a wave by an isolated atom. The atomic form factor depends on the type of scattering, which in turn depends on the nature of the incident radiation, typically X-ray, electron or neutron. The common feature of all form factors is that they involve a Fourier transform of a spatial density distribution of the scattering object from real space to momentum space (also known as reciprocal space). For an object with spatial density distribution, , the form factor, , is defined as , where is the spatial density of the scatterer about its center of mass (), and is the momentum transfer. As a result of the nature of the Fourier transform, the broader the distribution of the scatterer in real space , the narrower the distribution of in ; i.e., the faster the decay of the form factor. For crystals, atomic form factors are used to calculate the structure factor for a given Bragg peak of a crystal. X-ray form factors X-rays are scattered by the electron cloud of the atom and hence the scattering amplitude of X-rays increases with the atomic