It must be noted that the plot above is simply the normalized yield at each channel number from a thin dPS layer (about 200 Angstroms) on top of a thick PS. Normalized yield is usually the number of atoms detected. Channeling, however occurs when a beam of ions is carefully aligned with a major symmetry direction of a single crystal, such as a crystal axis or a plane. In this condition, most of the beam is steered through the channels formed by the string of atoms. Channeled particles cannot get close enough to the atomic nuclei to undergo scattering. Several mathematical operations were then performed, electronically, to obtain a concentration versus depth-profile as shown below in figure 17. Please refer to the source for detailed explanation of the mathematical equations.