Fourier transform infrared spectroscopy vibration modes

Fourier-transformed infrared spectroscopy (FT1R), either in the transmission mode(70), the grazing incidence reflection (GI) mode(7,5) or the attenuated total reflection (ATR) mode(7,2), has been the most widely used experimental tool for the characterization and structure determination of SA monolayers. GI-IR is especially useful in determining the molecular orientation in the film structures because it senses only the vibrational component perpendicular to the substrate surface(7,5). Polarized ATR-IR can also be used to study molecular orientation(7,77). McKeigue and Gula-ri(72) have used ATR-IR to quantitatively study the adsorption of the surfactant Aerosol-OT. 

Vibrational spectroscopy provides an excellent tool for examining interfacial properties. Experiments have been carried out using both the infrared and Raman techniques [12-14]. Discussion is limited here to Fourier transform infrared spectroscopy (FTIR) in the reflection mode. It is important to understand how the infrared radiation interacts with dipolar adsorbates at the interface. Consider an electromagnetic wave travelling in the (x, z)-plane, which strikes the interface located in the (x, y)-plane at an angle 0 with respect to the interface (see fig. 10.7). The electrical field vector associated with the wave can be resolved into two components, one oscillating in the (x, z)-plane (the parallel or p-component)... 

Fourier-transform infrared spectroscopy (FTIR) monitors changes in the IR vibrational absorption spectrum as a molecule diffuses from a terrace site to a step or other smface defect [92Heil]. The temporal change in the vibrational mode of interest can be used to deduce the diffusivity. 

Leonhard, M., Mantele, W. Fourier-transform infrared spectroscopy and electrochemistry of the primary electron donor in Rhodobacter sphaeroides and Rhodopseudranonas viridis reaction centers. Vibrational modes of the pigments in situ and evidtmce for protein and water modes affected by formation. Biochemistry 32,4532—4538 (1993)... 

Phase separation and spatial organization of membrane domains determine the state of water, fundamental interactions in the polymer/water/ion system, vibration modes of fixed sulfonate groups, and mobilities of water molecules and protons. Dynamic properties of the membrane can be probed at the microscopic scale with spectroscopic techniques, including Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) (Mauritz and Moore, 2004). FTIR... 

Fourier-transform infrared (FTIR) spectroscopy Spectroscopy based on excitation of vibrational modes of chemical bonds in a molecule. The energy of the infrared radiation absorbed is expressed in inverse centimeters (cm ), which represents a frequency unit. For transition-metal complexes, the ligands -C N and -C=0 have characteristic absorption bands at unusually high frequencies, so that they are easily distinguished from other bonds. The position of these bonds depends on the distribution of electron density between the metal and the ligand an increase of charge density at the metal results in a shift of the bands to lower frequencies. 

In order to characterize the MgO sites where the Pd atoms are stabilized after deposition by soft-landing techniques, we used CO as a probe molecule [61]. The adsorption energy, Eb, of CO has been computed and compared with results form thermal desorption spectroscopy (TDS). The vibrational modes, (o, of the adsorbed CO molecules have been determined and compared with Fourier transform infrared (FTTR) spectra. From this comparison one can propose a more realistic hypothesis on the MgO defect sites where the Pd atoms are adsorbed. 

Infrared-based techniques are used to identify molecules on the surface. IR radiation is used to excite vibrational modes in molecules in the gas phase or adsorbed on a surface. The transmitted or reflected IR spectrum can be analyzed in a spectrometer. Considerable improvement in the sensitivity can be achieved by use of Fourier transform infrared (FTIR) spectroscopy. Attenuated total reflection (the ATR-FTIR method) inside a crystal (germanium) of high refractive index can be used to further enhance the surface sensitivity (using the evanescent field). 

From an experimental standpoint, information on the dye binding modes at the semiconductor/dye interface, are conventionally accessed by vibrational spectroscopy [Fourier Transform InfraRed (FT-IR) spectroscopy and Surface-Enhanced Raman Spectroscopy (SERS)] [228-237]. These techniques can provide structural details about the adsorption modes as well as information on the relative orientation of the molecules anchored onto the oxide surface. Photoelectron Spectroscopy (PES) has also been successfully employed to characterize the dye/oxide interface for a series of organic dyes [238-242]. The analysis of the PES spectra yields information on the molecular and electronic structures at the interface, along with basic indications of the dye coverage and of the distance of selected atoms from the... 

Many aspects of surface science and surface spec troscopy are concerned with the geometrical structure of surfaces, the composition of the surface and the identification of adatoms that may be present. Vibrational spectroscopy is a method for direct measurement of specific chemical bonds of adsorbed atoms and molecules, both between the adsorbate and the surface and the adatoms themselves. In the early days of HREELS, the 1970s, an added attraction for this type of spectroscopy was the ability to observe adsorbate surface bonding modes (often <125 meV = 1000 cm ), because the infrared spectrometers of the day used grating spectrometers, and IR detectors that were useful only above 1600 cm . The low cost and versatile Fourier transform infrared spectrometer (FTIR) and improved detector technology have eclipsed HREELS for routine surface chemical bond analysis. There are, however, some surface processes that can only be observed with electrons. Some diagnostic benefits that are related to the scattering mechanisms operative in HREELS continue to be useful for surface science. It should be noted that HREELS is usually performed on a known adsorbate, with a focus on the details of a specific adsorption system. HREELS is seldom used for the identification of unknown adsorbate species. 

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