Thermally-Induced and Electron-Induced Chemistry of CF3I on Ni(100)

We have investigated the thermally-induced and electron-impact-induced chemistry of CF[sub 3]I on Ni(100) following adsorption at 100 K. The data support a model for the thermally-induced chemistry, in which CF[sub 3]I dissociates to CF[sub 3] and I, either upon adsorption or at slightly-elevated temperatures. Most CF[sub 3] decomposes to adsorbed C and F. Above 75% saturation of the first layer, the availability of surface sites for decomposition decreases to a level where some adsorbed CF[sub 3] remains intact and desorbs as such. Bombardment of multilayer CF[sub 3]I by low-energy electrons introduces new chemistry. Electron-induced decomposition (EID) of the parent molecule occurs through both C-I and C-F bond scission, with a measured cross section of 1.5 x 10[sup -16] cm[sup 2] (upper limit). Thermally-induced desorption from the electron-bombarded surface indicates a number of EID fragment reactions, most notably carbon-carbon bond formation, as evidenced by C[sub 2]F[sub 3]I[sup 1], C[sub 2]F[sub 4][sup +], C[sub 2]F[sub 5][sup +], C[sub 3]F[sub 3][sup +], and C[sub 4]F[sub 7][sup +]. To our knowledge, this is the first report of C-C bond formation in small fluorocarbons adsorbed on metal surfaces. 36 refs., 13 figs.