Interferometric investigation of the effects, on the refractive index of 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 refractive index of such a film. The refractive index of pure polyvinyl alcohol (PVA) film and five PVA films, doped with lead acetate of concentrations 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 increases with increasing the concentration of doped lead acetate. After irradiation the refractive index increases with increasing the dose up to a certain limit then decreases again. This indicates that the radiation deformation of gamma radiation is a chain scission effect.