Abstract
Studying surface reactions using ultrafast optical pump and x-ray probe experiments relies on accurate calculations of x-ray spectra of adsorbates for the correct identification of the spectral signatures and their dynamical evolution. We show that experimental x-ray absorption can be well reproduced for different binding sites in a static prototype system CO/Ni(100) at a standard density functional theory generalized-gradient-approximation level of theory using a plane-wave basis and pseudopotentials. This validates its utility in analyzing ultrafast x-ray probe experiments. The accuracy of computed relative core level binding energies is about 0.2 eV, representing a lower limit for which spectral features can be resolved with this method. We also show that the commonly used Z + 1 approximation gives very good core binding energy shifts overall. However, we find a discrepancy for CO adsorbed in the hollow site, which we assign to the significantly stronger hybridization in hollow bonding than in on-top.
Highlights
Surface-sensitive x-ray techniques represent an invaluable tool in surface science
Studying surface reactions using ultrafast optical pump and x-ray probe experiments relies on accurate calculations of x-ray spectra of adsorbates for the correct identification of the spectral signatures and their dynamical evolution
We show that experimental x-ray absorption can be well reproduced for different binding sites in a static prototype system CO/Ni(100) at a standard density functional theory generalizedgradient-approximation level of theory using a plane-wave basis and pseudopotentials
Summary
The tunability and intensity of modern synchrotron sources result in high-resolution x-ray spectra, allowing the identification of adsorbed atomic and molecular species, as well as their adsorption sites. /or desorption from it, can be initiated using an ultrashort optical laser pulse, while a probing x-ray pulse with a duration of ∼10 fs gives time-resolved spectra during the evolution of the system, with subps resolution.. /or desorption from it, can be initiated using an ultrashort optical laser pulse, while a probing x-ray pulse with a duration of ∼10 fs gives time-resolved spectra during the evolution of the system, with subps resolution.3–7 This has led to a new understanding of surface reaction pathways.. When moving toward systems relevant for industrial catalysis, the number of intermediates and non-equilibrium structures in the given reaction can be high and reliable simulations of the spectra are crucial
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