The Journal of Chemical Physics · 1994 · 140 citations · 37 references
X-ray SpectroscopyEngineeringChemistrySoft MatterElectronic Excited StatePolymer MaterialElectronic StatesIon EmissionRadiation ChemistryPolymer ChemistryMaterials SciencePhotochemistryAtomic PhysicsPhysical ChemistrySoft X-ray ExcitationsQuantum ChemistrySynchrotron RadiationSite Specific FragmentationRydberg OrbitalPolymer SolutionNatural SciencesSurface SciencePolymer ScienceApplied PhysicsPolymer PropertyThin FilmsMolecular Fragmentation
Soft x-ray excitations in the 250–600 eV photon energy range on poly(methylmethacrylate) (PMMA) result in ionic fragmentation of the original polymer with the most intense ions corresponding to CH+3, H+, CH+2, CH+, CHO+, and COOCH+3. The photon energy dependence of ion desorption from thin films of PMMA was measured to investigate the primary steps in radiation induced decomposition following carbon and oxygen 1s electron excitations using monochromatic pulsed-synchrotron radiation. It was clearly found that the decomposition depends on the nature of the electronic states created in the excited species. The fragmentation pattern changes depending on the transitions of the 1s electron to a Rydberg orbital, an unoccupied molecular orbital or the ionization continuum. Moreover, the fragmentation occurs specifically around the site of the atom where the optical excitation takes place. Excitations from carbon and oxygen 1s to σ* states seem to be specially efficient for ion production as observed in the case of CH+3, CH+2, and CH+ at 288.7 and 535.6 eV, and in the case of CHO+ at 539.3 eV.
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Site-Specific Fragmentation of Small Molecules Following Soft-X-Ray Excitation
W. Eberhardt, T. K. Sham, R. Carr et al. · Physical Review Letters · 1983 · 267 citations