Electron Core-Hole Interaction and Its Induced Ionic Structural Relaxation in Molecular Systems under X-Ray Irradiation

The experiments on perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride and 16FCuPc on Ag(111) surfaces by the normal incidence x-ray standing wave are poorly reproduced by first-principles ground state calculations but well reproduced by considering initial- and final-state effects, which include the response of the valence electrons to screen a core hole created by x-ray photoemission and further induced ionic structural relaxation. This study shows that the initial- and final-state effects due to screening are of great importance in characterizing molecules on metal surfaces in the normal incidence x-ray standing wave experiments.

Figure 1

Top view (top), side view (middle), and front view (bottom) of the calculated molecular geometries of PTCDA on Ag(111) in (a) the ionic initial state, (b) the ionic final state with a core hole created on carboxylic O1, and (c) on anhydride O2. E-O means the excited oxygen atom.

Figure 2

Structures of (a) 16FCuPc and (b) 16FCuPr. (c) Top view and (d) side view of the fully relaxed adsorption geometry of 16FCuPr on Ag(111). The side view of the calculated geometry by $0.5e$ final-state approximation with a 0.5 hole created (e) on F1 and (f) on F2, respectively.