Reactions in nanofilms of trifluoroacetic acid (CF3COOH) driven by low energy electrons

Electron stimulated desorption (ESD) of fragment anions and thermal desorption spectroscopy (TDS) is applied to study reactions in thin films of a few CF3COOH/CF3COOD monolayers following low energy electron impact (0-20 eV). In ESD, the fragment ions H−/D− and F− are observed via resonant features in the energy range 5-12 eV similar to the dissociative electron attachment (DEA) resonances present in gas phase CF3COOH. Extended electron irradiation of the film at energies above 9 eV generates CO2 and CHF3/CF4 as revealed by a combination of TDS and ESD experiments. The yield for these reactions continuously increases with energy indicating that they are initiated via electronically excited neutrals rather than negative ion resonances. No reactions induced by sub-excitation electrons (≈1 eV) could be observed using the present experimental techniques. In a very recent study on electron attachment to clusters of CF3COOH [J. Langer, I. Martin, G. Karwasz, E. Illenberger, Int. J. Mass Spectrom. Ion Processes 249/250 (2006), 477], the ion-molecule complex CF3COO−·H2O appeared as strongest signal via a resonance located at 0.4 eV.