Dissociative Electron Attachment to Gas- and Condensed-Phase CF3Cl: Anion Desorption and Trapping

The interaction of electrons in the energy range from near zero to 10 eV with CF3Cl physisorbed on a Kr surface is studied and compared with previous gas-phase experiments on isolated molecules and CF3Cl clusters. In the gas phase CF3Cl shows resonances in the dissociative attachment (DA) cross section at 1.4 eV, near 4−5 eV, and at 9 eV with the 1.4 eV feature assigned as a single particle resonance with a strong C−Cl repulsive nature. From adsorbed CF3Cl, we observe desorption of Cl- and F- with resonances in the cross section which can be correlated to the gas-phase DA features. Despite its antibonding nature, Cl- desorption via the single particle resonance is very weak, indicating that direct desorption processes do not occur; i.e., orientations of the molecule with the C−Cl axis pointing away from the surface can be excluded, and desorption is always preceded by postdissociation interactions. Charge trapping is virtually restricted to the low-energy resonance. Its maximum is at 0.8 eV and reflects t...