[en] Multicharged ions (Ag^q+, Cu^q+, Si^q+, q=1,2,3) at constant speed ∼v_Bohr (Bohr velocity) were used to irradiate PC (polycarbonate) foils which were subsequently chemically etched. Because of the low ion dose of <10⁸ions/cm², pores on the surface were discrete. The diameters of the pores were measured by means of scanning electron microscopy (SEM). From the linear dependence of the pore diameter on the etching time, the transversal etching rate can be obtained. It was found that the transversal etching rate decreased with ion charge. These results can mainly be explained by the variation of the charge exchange process for ions with a different charge state