Electron-stimulated desorption in organic molecular solids

Electron-stimulated desorption of H+ from solid cyclohexane, benzene, 1,2,3,–5 tetrafluorobenzene (C6H2F4), and nanofluoroisobutane [(CF3)3CH] and of F+ from solid C6H2F4 and (CF3)3CH are reported. H+ threshold energies are 25(±1)eV, ∼29 eV, 29 (±1) eV, and 27 (±1) eV for cyclohexane, benzene, C6H2F4, and (CF3)3CH, respectively. F+ thresholds are 38 (±1) eV for C6H2F4, and 40 (±1) eV for (CF3)3CH. This behavior is interpreted as being due to desorption from mainly multivalence-hole final states created by decay from single C 2s or F 2s holes. These multihole excitations are localized to the extent that excitations which break C–H bonds do not affect C–F bonds and vice versa. A weak CF+ threshold was observed at ∼40 eV with a large increase in yield at ∼53 eV. A change in slope occurs for the H+ and F+ yields from C6H2F4 near 55 eV and for the H+ and F+ yields from (CF3)3CH near 60 eV. These data, along with the increase in CF+ yield from (CF3)3CH at 53 eV suggest desorption can also occur following more complex multielectron excitations.