Observation of Fano line shapes in infrared vibrational spectra of CO2 adsorbed on Cu(997) and Cu(111)

Abstract

Adsorption states of carbon dioxide on the Cu(997) and Cu(111) surfaces were investigated by infrared reflection absorption spectroscopy, temperature programmed desorption, and X-ray photoelectron spectroscopy. CO2 molecules are physisorbed on the Cu(997) surface at temperatures below 70 K; neither chemisorption nor dissociation of CO2 occurs on the Cu(997) surface at this low temperature. However, the vibrational spectra of adsorbed CO2 depend significantly on the substrate temperature and coverage. IR spectra of CO2 vibrational modes at 70 K show asymmetric Fano line shapes, while only normal absorption bands are observed when CO2 is adsorbed at 20 K. Fano line shapes are also observed for CO2 on Cu(111) at 85 K. The observation of Fano effect indicates the coupling between the electronic continuum states of the Cu surface and the internal vibrational modes of CO2 even in such physisorbed system.

Adsorption of CO2 on Terrace, Step, and Defect Sites on Pt Surfaces: A Combined TPD, XPS, and DFT Study

“…The TPD measurements were carried out in an UHV chamber. − The system base pressure was 1.0 × 10 –10 Torr. The measurements were carried out on a Pt(997) surface, which consisted of ∼8.5 atomic rows of (111) terraces and a single (111) step (Figure S1, Supporting Information).…”

“…In the case of physisorbed species on metal surfaces, a photoelectron peak from the multilayer is observed at a higher binding energy than that of the monolayer (first layer) because of insufficient final state screening by the metal substrate. 30 Thus, the peak near 290.85 eV at 30 shots was assigned to multilayer CO 2 . The same behavior was observed in the O 1s spectra (Section S5, Supporting Information).…”

“…This is different from what occurs on Cu(997). 30 Further investigation is need to clarify the difference between CO 2 adsorption on Cu(997) and on Pt(997).…”

A Correction Scheme for Fano Line Shapes in Two-Dimensional Infrared Spectroscopy

“…Fano lineshapes were also observed on ordered crystalline surfaces due to the coupling of electronhole pairs and adsorbate vibrations. [25][26][27][28][29] A somewhat different example, also leading to distorted lineshapes, con-cerns the resonance Mie mechanism in diffuse reflection spectroscopy. 30 While Eq.…”

“…In SEIRA spectroscopy, Fano line shapes are the result of vibrational transitions interfering with the plasmon resonance. − The theory has been worked out for both nonresonant ,,− and resonant ,, SEIRA spectroscopy. Fano line shapes were also observed on ordered crystalline surfaces due to the coupling of electron–hole pairs and adsorbate vibrations. − A somewhat different example, also leading to distorted line shapes, concerns the resonance Mie mechanism in diffuse reflection spectroscopy …”