Charged particle activation analysis (CPAA) is able to analyze light elements such as carbon and oxygen at trace levels in semiconductor materials. This technique requires the knowledge of the stopping powers of these materials for channeled ions. The electronic energy loss for ions entering the crystal lattice in a random direction is well established. The electronic energy losses for protons, deuterons, 3 He + and 4 He + ions entering a 3.6 μm thick silicon single crystal along the <100> direction were measured by using the transmission of particles technique. Data obtained were compared with those obtained by other authors using theoretical and experimental methods.