Electron energy loss spectroscopy of pristine and radiation damaged polyethylene

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Abstract
The spectra of valence and core electronic excitations of polyethylene from 1 to 390 eV were measured with a resolution of 0.11 eV by transmission electron energy loss spectroscopy. Structure at 9.5, 13.2, 14.7, 16.6, 19.6, 21.6 eV and a continuum of core excitations beginning at 287.5 eV was measured and compared with theoretical calculations of molecular excitons and interband transitions. The momentum dependence of the fundamental absorption threshold at 7.2 eV indicates that the absorption edge is due to highly localized excitons. From the energy loss spectra the complex dielectric response function and optical properties were calculated and compared with existing optical data. Radiation induced changes in the electronic structure were observed by their characteristic excitation spectra which were shown to be due to formation of polyenyl chromophores in the polymer backbone.