Condensation coefficients of Ag on polymers

Using a novel very sensitive radiotracer technique, we have measured the condensation coefficient C of Ag on several polymers. C shows an extreme variation ranging from close to unity for polyimide to values as low as 0.002 for Teflon AF(TM) at room temperature. C decreases strongly at elevated temperatures and exhibits a drop somewhere below the bulk glass transition temperature. The observed angular distribution of reemitted atoms does not depend on the angle of incidence and has a cos theta form. This, among other arguments, suggests them to be adsorbed at the surface prior to reemission. Nucleation, studied on a polycarbonate, turned out to take place at preferred sites.