SYNCHROTRON-RADIATION AS A SCALPEL FOR MOLECULAR-SYSTEMS - EVIDENCE OF SITE-SPECIFIC CHEMICAL-BOND SCISSION OF PMMA BY OXYGEN IS ELECTRON-EXCITATION

CH3 + ion desorption by oxygen 1s electron excitation was studied for thin solid films of poly (methyl methacrylate) (PMMA), poly (methyl ac rylate) (PMA), and poly (methacrylic acid) (PMAA) in order to determin e the chemical site responsible for the CH3 + ion desorption in PMMA. We compared the photon energy dependencies of CH3 + ion yields from th ese three polymers and verified that the excitation of the oxygen 1s e lectron at OCH3 to sigma state localized at COCH3 in PMMA results in the effective emission of CH3 + ions by fragmentation at the side chai n and not at the main chain. The results demonstrate that there is a s trong correlation between the sites of the excitation and the chemical -bond scission, and that monochromatic synchrotron radiation can be us ed as a scalpel for a molecular system.