*2.2.1 When the angle between ionic and damaged atomic momentum vector is 90°*

As indicated by event C in **Figure 5**, the maximum feasible angle between the ion's actual momentum vector and the subsequent momentum vector of the affected/damaged atom is 90°, and the momentum vector of the hit atom is zero. In this instance, as a direct outcome of the basic collision, surface atoms cannot acquire the velocity components in the direction away from the surface. A primary collision will result in at least one and usually two secondary collisions, all of which will be close to the surface.
