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

Mass spectrometry has been used as an analytical tool in determining t he species and relative quantities of volatile reaction products gener ated during destruction of the polymer PMMA by ion implantation. Speci fically, one very important objective was to try to relate the radiati on chemistry with the radiation physics of fundamental track formation . Experiments are described in which the depth distribution of the emi ssion of volatile products was determined for irradiation of PMMA with 35MeV Li-7(2+) ions. The mass spectral measurements of the reaction p roducts were carried out on thin PMMA foils as a function of the angle of beam incidence, and hence of penetration depth. Correlation of the differences in mass spectra with the foil number yielded the depth di stribution of degassing. Comparison with theory shows that degassing o f volatiles, which is itself a consequence of multiple chain scission, can be related to the electronic rather than nuclear energy transfer processes. The detailed shape of the measured degassing distribution d iffers somewhat from that expected from theory. This clearly points to inherent inadequacies in any simple model for polymer destruction.