here, "α" and "β" are the incidence angles of the beam and exit angle of the recoiling ion respectively, connected to the scattering angle "ϕ" by "ϕ=α+β". It should be noticed here that the depth resolution depends on the relative energy resolution only, as well as the relative stopping power of incoming and outgoing ions. The detector resolution and energy broadening associated with the measuring geometry contribute to the energy spread, "δE". The detector acceptance angle and the finite beam spot size define a scattering angle range "δϕ" causing a kinematic energy spread "δEkin" according to equation 6: