High energy ion induced decomposition and diffusion in thin polymer films.

Electronic excitation in thin polymer films by MeV ion beams and on-line transient mass spectroscopy together provide a new opportunity for measuring the diffusion of molecules in polymers even when the diffusion coefficients are ~(-10)cm (2)s(-1). With a quadrupole mass spectrometer, we have obtained transients of several molecular species from a variety of polymers bombarded by 2 MeV helium and argon ions. We have measured, for example, transient emission of D2, CO, CO2, CD3OD, etc. , from deuterated Poly (methyl methacrylate), PMMA. The beam fluences required for the measurements are sufficiently small that they cause minor perturbation in the structure of the film. The exciting ion pulse is typically 15 seconds wide with fast (