The accuracy of kinetic reaction parameters for surface reactions derived from real-time X-ray Photoelectron Spectroscopy (XPS) is questioned. Experimental data are simulated with exactly known pre-exponential A and activation energy E_a, thinned out, overlaid with noise and then fitted using grid searches. This procedure reveals ambiguities, especially for the common linear temperature ramps.

Abstract

The kinetics of coupling reactions on surfaces can be quantitatively studied in real time by X-ray Photoelectron Spectroscopy (XPS). From fitting experimental data, kinetic reaction parameters such as the rate constant's pre-exponential and activation energy can be deduced and compared to quantum chemical simulations. To elucidate the possibilities and limitations of this approach, we propose studies in which experimental data are first simulated and subsequently fitted. Knowing the exact kinetic parameters used in the simulation allows one to evaluate the accuracy of the fit result. Here, several experimental influences, such as the data point density and the addition of noise, are explored for a model reaction with first-order kinetics. The proposed procedure sheds light on the accuracy with which kinetic parameters can be derived and may also help in the design of future experiments.