Elektroneninduzierte Reaktionen in dünnen organischen Molekülfilmen

Abstract

This work provides an insight in the mechanisms of electron-induced reactions of thin films. For this, different organic substances were investigated using HREEL spectroscopy and products formed during bombardment were identified. Most of the substances are modified significantly when the incident electron energy is increased above 10 eV.Simple hydrocarbons like methane, ethane and ethylene seem to be relative stable with respect to electron bombardment. Aldehydes (acet- (AA), propion- (PA) and butyraldehyde (BA)) release CO. Other fragments formed together with CO react with adjacent molecules to a produce longer aldehydes. In the case of cyclic ethers (ethlyeneoxide (EO) and tetrahydrofurane (THF)), the main product is an aldehyde which reacts further to yield CO and unsaturated products. Other less prominant products are alcoholic substances or the enolic form of the aldehyde. After longer bombardment of EO a network is formed.In addition, cross sections were determined in the case of THF to give information about a reaction sequence. It was shown, that CO is not only formed from the initially produced aldehyde but also from THF itself.The investigation of gamma-butyrolactone (GBL) aimed at linking known gas phase results to the condensed phase. A charging during bombardment with low-energy electrons indicates the production of negative intermediates in the condensed phase. However, no products could be identified unequivocally. At high energies the formation of ethylene was observed and ascribed to successive CO release, with PA as intermediate.Finally acetonitrile was studied as a potential agent for the functionalization of surfaces during bombardment with electrons. The chemisorption of CH2CN fragments on diamond through Cdiam-C and Cdiam-N linkages was observed and a reaction mechanism was formulated.