# 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 ${\displaystyle \scriptstyle I(q)}$, 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):

{\displaystyle {\begin{alignedat}{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{alignedat}}}

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, ${\displaystyle \scriptstyle I(q)}$, is what is measured experimentally on a detector (including a possible background). However, this quantify is frequently converted into (or treated as), ${\displaystyle \scriptstyle P(q)}$ or ${\displaystyle \scriptstyle S(q)}$, in order to perform further analysis.