INTERFEROMETRIC INVESTIGATION OF THE EFFECTS, ON THE REFRACTIVE-INDEXOF PVA, OF DOPING WITH LEAD ACETATE AND GAMMA-IRRADIATION

Non-localized interference fringes, resulting from illuminating a film of PVA with a laser point source, have been used for measuring the re fractive index of such a film. The refractive index of pure polyvinyl alcohol (PVA) film and five PVA films, doped with lead acetate of conc entrations of 5, 10, 15, 20 and 25% by weight, have been investigated before and after irradiation by doses of 2, 4, 6, 8 and 10 Mrad gamma rays. It is found that, before irradiation, the refractive index incre ases with increasing the concentration of doped lead acetate. After ir radiation the refractive index increases with increasing the dose up t o a certain limit then decreases again. This indicates that the radiat ion deformation of gamma radiation is a chain scission effect. (C) 199 7 Elsevier Science Ltd.