# Scattering intensity

The scattering intensity is the amount of radiation (e.g. x-ray or neutron) scattered at any particular angle. This quantity is usually given by $\scriptstyle I(q)$, where q is the momentum transfer (a vector in reciprocal-space).

## Contributions

The scattering intensity is frequently divided into the contribution from the form factor (F or P) and structure factor (S):

\begin{alignat}{2} I(q) & = \langle |F(\mathbf{q})|^2 S(\mathbf{q}) \rangle \\ & = P(q) \left\langle \frac{|F(\mathbf{q})|^2}{P(q)} S(\mathbf{q}) \right\rangle \\ & = P(q)S(q) \end{alignat}

The form factor describes the shape of scattering objects, whereas the structure factor describes the organization of these objects (disordered, in a lattice, etc.). The scattering intensity, $\scriptstyle I(q)$, is what is measured experimentally on a detector (including a possible background). However, this quantify is frequently converted into (or treated as), $\scriptstyle P(q)$ or $\scriptstyle S(q)$, in order to perform further analysis.