The negative ion yields φ (H?) and the neutral atom yields φ (H) of 0.6, 0.9, 1.2, 1.6 and 1.8 MeV H+ projectiles traversing various carbon foils have been measured. The experimental results showed that neither φ(H?) nor φ(H) varies with the dwell time ^ at the same energy. φ(H)is larger than φ(H?) by about 3–4 orders of magnitude. The charge exchanging between H+ ions and carbon foils was analyzed. It can be seen that the charge exchange is the most basic process. The experience formula of σc/σl has been gotten.
