Positron annihilation lifetime and gas permeation studies of energetic ion-irradiated polycarbonate membranes

The polycarbonate membranes of 40-50 μm thicknesses were prepared by the solution cast method. These films were irradiated by a 60 MeV, C5+ ion beam with the fluence of 5×106, 4×108 and 1×1012 ions cm−2. The ion beam effects were studied by the positron annihilation lifetime technique. The ortho-positronium (o-Ps) lifetime shows an increase with the ion dose 5×106, 4×108 ions cm−2. For the films irradiated to the fluence of 1×1012 ions cm−2, the o-Ps lifetime falls to the lower value. The results are interpreted in terms of change in the free volume. The gas permeability measurements also indicate an increase in the free volume in the samples irradiated upto the fluence of the 4×108 ions cm−2.