HIGH-RESOLUTION X-RAY ABSORPTION-SPECTROSCOPY OF LINEAR HYDROCARBONS ADSORBED ON NOBLE-METAL SURFACES

Recent progress in the performance of soft x-ray monochromators has revealed new features in soft x-ray molecular photoabsorption spectra. We present here a comprehensive high resolution x-ray absorption study on the linear hydrocarbons C2H2n and C2D2n, adsorbed on Ag(100) and Cu(100) at 50 K and in the solid and the gas phase. A line shape analysis is given, for the bound as well as for the continuum resonances and the absorption thresholds, by means of models easily accessible to the experimentalist, leading to a quantitative understanding of the observed spectra, including the vibrational envelopes. Changes in intramolecular bond lengths upon core-hole excitation can be determined and tracked as a function of deuteration and chemisorption. The effects of the substrate bonding on the vibrational envelopes are analyzed.