Vibrational spectroscopy at interfaces by IR-VIS sum-frequency generation using CLIO FEL

Conference · Sun Dec 31 04:00:00 EST 1995

DOI:https://doi.org/10.1016/0168-9002(95)01219-2· OSTI ID:238720

Peremans, A; Tadjeddine, A; Wan Quan, Z ^[1]

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1. LURE, Orsay (France); and others

IR-vis sum-frequency generation (SFG) has developed into a versatile technique for probing the vibrational structure of interfaces. To overcome the limited spectral range accessible by benchtop IR lasers, we have developed an SFG spectrometer that makes use of the broad band tuneable infrared beam provided by the CLIO-FEL. We will evaluate the gain in sensitivity of the FEL-SFG spectrometer in comparison to that of benchtop lasers, taking account of the surface damage by laser heating. Thereafter, we review the different research projects undertaken using this facility: (1) The interface selectivity of SFG makes it particularly suitable for probing buried liquid/solid interface. We took advantage of the spectrometer sensitivity to monitor the electrochemical deposition of hydrogen on platinum single crystals at under- and overpotential (2) Because of its sensitivity to the molecular symmetry, SFG allows probing the conformation of self assembled monolayers deposited on metals. We discuss SFG spectra of {omega}(4-nitroanilino)-dodecane adsorbed on polycrystalline gold and silver films; in the 1550 - 900 cm{sup -1} spectral range. (3) We have undertaken a spectroscopic approach for the investigation of polymer films adhesion on glass. Polyurethane/glass interface is investigated in the 2200 - 1600 cin{sup -1} spectral region. (4) The use of the CLIO FEL allows probing of the vibrational dynamics of the prominent IR active vibrations between 1500 and 500 cm{sup -1} of fullerene epitaxial films. These modes are modified upon charge transfer from the substrate to the C{sub 60} molecules. Preliminary SFG spectra of C{sub 60}/Ag interface are presented. (5) Site specific detection of CO adsorption and CO + O coadsorption on Pd(111) are studied.

• Research Organization: Brookhaven National Lab., Upton, NY (United States)
• OSTI ID: 238720
• Report Number(s): BNL--61982-Absts.; CONF-9508156--Absts.; ON: DE96002729
• Country of Publication: United States
• Language: English

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