IRRADIATION OF PMMA WITH HIGH-ENERGY LIGHT-IONS - THE DEPTH DISTRIBUTION FOR VOLATILE REACTION-PRODUCT EMISSION

Mass spectrometry has been used as an analytical tool in determining t he species and quantities of volatile reaction products generated duri ng destruction of polymers by ion implantation. Specifically, one very important objective was to relate the radiation chemistry with the ra diation physics of fundamental track formation. Experiments are descri bed in which the depth distribution of the emission of volatile produc ts has been determined for irradiation of PMMA with 35MeV Li-7(2+) ion s. The mass spectral measurements of the reaction products were carrie d out on thin PMMA foils as a function of the angle of beam incidence, and hence of penetration depth. Correlation of the differences in mas s spectra with the foil number yielded the depth distribution of degas sing. Comparison with theory shows that volatile gas degassing, which is itself a consequence of multiple chain scission, can be related to electronic rather than nuclear energy transfer processes. However, the detailed shape of the measured degassing distribution differs from th at expected from theory. This clearly points to inherent inadequacies in the simple model for polymer destruction.