Low-energy electron scattering cross section for the production of CO within condensed acetone

We report on the low-energy electron induced production of CO within thin solid films of acetone condensed at low temperature on a solid Ar substrate. The CO fragments, which remain trapped within the bulk of the acetone film, are detected in situ via their first electronic state a (3)Pi using high-resolution electron-energy-loss spectroscopy. The production of CO is studied as a function of the electron energy (2-25 eV), electron dose, and film thickness. The energy dependence of CO production is calibrated in terms of an electron scattering cross section sigma(p). It is characterized by an energy threshold at 8 eV, a strong rise up to about 14 eV, and a broad maximum of sigma(p) approximate to 6.8 x 10(-17) cm(2) at 16 eV followed by a relatively small and monotonous decrease up to 25 eV. The production of CO is discussed in terms of the formation of several core-excited electron resonances, which may lead directly to the fragmentation of the molecule via dissociative electron attachment or indirectly by decaying into an entirely repulsive part of the corresponding neutral excited state and positive ion states. (C) 2000 American Institute of Physics. [S0021-9606(00)00533-X].