Na-induced bonding and bond-length changes for CO on Pt(111): A near-edge x-ray-absorption fine-structure study.

Abstract

Near-edge x-ray absorption fine-structure studies above the C and O K edges for CO on Pt(111) reveal a 4-eV shift of the \ensuremath{\sigma} shape resonance when Na(0.2 monolayer) is coabsorbed. This allows determination of a Na-induced (0.12\ifmmode\pm\else\textpm\fi{}0.03)-A\r{} expansion of the C-O bond. Na does not affect the vertical molecular orientation on the surface. Reduction and broadening of the 1s\ensuremath{\rightarrow}2${\mathrm{\ensuremath{\pi}}}^{\mathrm{*}}$ resonance and the CO bond lengthening in the presence of Na signifies substantially increased metal to CO backbonding.