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# Basic neutron scattering

You may recall the Bragg law from your high school physics

giving the scattering condition for a wave of wavelength against a series of lattice planes with lattice spacing , rotated the angle off the lattice plane normal. is an integer giving the spectral order of the scattered wave. In neutron science one often refers to the scattering vector, of a given reflection, where

This gives us the scattering vector formulation of the Bragg law

where . The Bragg law / scattering condition is illustrated in Figure 1.

Figure 1: Illustration of the Bragg Law.

Most of the neutron processes we will study in this paper are elastic, meaning that the wavelength of the neutron is unaltered by the process.