Multiple-scattering and DV-X_α theoretical determination of the local structure of SO₂/Pd(111)

We have calculated the sulfur 1s near-edge x-ray absorption fine-structure (NEXAFS) spectra of SO₂ adsorbed on Pd(111) in terms of the multiple-scattering cluster and self-consistent field DV-X_α method. The physical origin of the resonances in the NEXAFS spectra has been unveiled. By the multiple-scattering calculation we have for the first time identified two weak features appearing in S K-shell NEXAFS of SO₂/Pd(111), which locate near the π* and σ* resonances respectively. Meanwhile, a self-consistent DV-X_α cluster calculation has been performed to confirm the above conclusion. Our calculation results for the local structure of SO₂/Pd(111) are broadly in agreement with those of Fourier-transform analysis of the surface-extended x-ray absorption fine structure.