The determination of binding energies and preexponential factors: a time resolved HREELS study on Fe(1 1 1)/CO2

Characteristic high-resolution-electron-energy-loss-spectroscopy (HREELS) intensities of the linear CO2-state on Fe(1 1 1) have been measured for several different CO2 pressures as function of surface temperature (temperature programmed HREELS). Taking these isobaric data as input into the Clausius-Clapeyron equation yields a set of isosteric binding energies as function of coverage, which follow the linear relation Eb = Eb0 ∗ (1 − 0.168 ∗ θ) quite closely. In order to achieve a complete description of the system, the isothermal response to CO2 pulses was monitored versus time for temperatures between 100 K and 135 K (time resolved HREELS). From these data the adsorption—and the desorption coefficients were determined as function of temperature and coverage by fitting the experimental data to an adsorption model. With the isosteric binding energies as input into the Arrhenius parameterisation of the desorption coefficients a set of preexponentials has been determined as function of temperature. Their values range between 2 × 1013/s to 1015/s.