Vibrational fine structure on C 1s core-level photoemission: Ni(1 1 1)–ethyne and Ni(1 1 1)–2-butyne

Abstract

High-resolution core-level photoemission measurements for ethyne (HCCH) and 2-butyne (H 3C–CC–CH 3) on the Ni(1 1 1) surface reveal the presence of vibrational excitations for both adsorbates, similar to those observed in recent gas-phase core-level photoemission investigations. The vibrational line splitting for ethyne is 300±50 meV ( 2400±400 cm −1 ). A binding energy difference of approximately 0.7 eV was observed for the 1s core levels of the inequivalent C atoms in a monolayer of 2-butyne. The vibrational line splittings are 370±20 meV ( 2980±160 cm −1 ) and 250±30 ( 2020±240 cm −1 ) meV for the 289.56 and 288.80 eV core levels, respectively. In addition, preliminary energy-scanned photoelectron diffraction (PED) measurements were performed on a monolayer of 2-butyne. A comparison between the modulation functions of 2-butyne and previously measured ethyne indicates similar local structures for these adsorbates. Furthermore, the PED measurements reveal that the 288.80 eV C 1s line can be assigned to the central C atoms that participate in the bonding to the surface.