Polycarbonate membranes of thickness 18 pm were irradiated by Ni7+ ion of 100 MeV at fluences 10(6)-10(8) ions/cm(2). The permeability for hydrogen and carbon dioxide has been measured from the membrane with increasing etching time. Permeability of both the gases increases with etching time, but for hydrogen the permeability was higher than for carbon dioxide for all membranes. The selectivity of hydrogen increases as ion fluence of membrane increases, for 10(8) ions/cm(2) membrane was higher than the lower fluence membranes. The irradiated membranes were also etched by monitoring the current, which shows change in the etching time for membrane of different doses. Ion permeation measurements show that pores in polymeric membrane are charged or neutralized, which depends upon the variation in concentration of the solvent. The etched tracks of membranes were characterized by the scanning electron microscopy. (c) 2006 Wiley Periodicals, Inc.