Infrared absorption spectroscopy IRAS

The atomic density of the (1 x 1) surface is 1.28 x lO Pt atoms cm [39]. This is approximately 25% lower than the atomic density of the (hex) phase (i.e., 1.61 x lO Pt atoms cm [47]). This density difference results in significant mass transport of platinum atoms during the back-reconstruction. Scanning tunneling microscopy (STM) data demonstrate [47-49] that expelled platinum atoms form clusters with size of 15-25 A. The clusters are randomly distributed within the CO-islands boundaries. Infrared absorption spectroscopy (IRAS) [42,43] and HREELS [31,44,45] have shown the existence of two molecularly adsorbed CO species on the surface of the (1 x 1) islands in bridge (CObr) state and in the on-top (COtop) state. The saturation coverage of CO on the Pt(l 0 0) surface at 300 K, estimated by a nuclear microanalysis, is 0.75 ML [39]. 

In the fields of solid-state and molecular physics, there have been many different experimental techniques introduced for vibrational spectroscopy. However, the investigation of the vibrational properties of bare solid surfaces is dominated by the two techniques of helium atom scattering (HAS) and high-resolution electron energy loss spectroscopy (HREELS). Both have been used to map surface phonon dispersions. In addition, that is, optical techniques such as infrared absorption spectroscopy (IRAS) (Chapter 3.4.1) and recentiy also inelastic tunneling... 

We wondered why NSCs proliferated exclusively on surfaces with EGF-His ligands anchored by coordination. We focused on two aspects in particular the conformational integrity of coordinated EGF-His and the stability of coordinate bonds at the interface. Conformational information was acquired with multiple internal reflection-infrared absorption spectroscopy (MIR-IRAS) [97]. The stability of coordinate bonds was assessed by culturing NSCs on a surface with a small region of EGF-His ligands anchored by coordination. This spatially restricted EGF-His anchoring enabled an intuitive exploration of EGF-His release under cell culture conditions. 

Figure 10.20 (A) Temperature-programmed desorption (TPD) and (B) Infrared reflection absorption spectroscopy (IRAS) spectra of CO adsorbed on Au/FeO(111) as a function of Au coverage. (Reprinted from Lemire, C. et al., Angew. Chem. Int. Ed., 43, 118-121,2004. With permission from Wiley-VCH.)...

Amino-amido-thiol HS —(CH2)io CO— NH—CH2—NH2 adsorbed on Au(lll) has been studied by sum frequency generation and infrared reflection absorption spectroscopy (IRAS) in the CH2 stretching vibration region [151]. 

Many similar studies have been done at surface science conditions using step-function concentration signals. For example, Takagi et al. (52) studied the adsorption and desorption of CO on Ni(lOO) via infrared reflection absorption spectroscopy (IRAS). In one case, CO dosing was turned on for 214 s and then turned off. The response of the spectrum of the surface intermediate was followed by IRAS. Of course, under these high-vacuum... 

On metal surfaces, two additional selection rules apply. The first is that only vibrations perpendicular to the surface are HREELS active. This rule follows from two phenomena unique at metal surfaces (i) Electromagnetic waves polarized perpendicularly to the plane of incidence (parallel to the plane of the surface) undergo a 180° phase shift upon reflection. That is, at the metal surface, the out-of-phase electric-field vectors of the incident and reflected waves cancel each other as a result, no field exists that can couple with dipoles that oscillate parallel to the surface, (ii) The dynamic dipole moment generated by an oscillator that vibrates in the surface-parallel direction is cancelled by that of its image dipole (Figure 1) hence, there the net dynamic dipole moment is zero. On the other hand, if the real dipole is oriented perpendicularly to the surface, its dynamic dipole moment is reinforced by that of its image dipole. This selection rule is the same as that for infrared reflection-absorption spectroscopy (IRAS). =... 

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) Reflection-absorption infrared spectroscopy (RAIRS) (also known as infrared reflection absorption spectroscopy, IRAS or IRRAS) Multiple Internal reflection spectroscopy (MIR)... 

Infrared Reflection Absorption Spectroscopy (IRAS) Measurements. The IRAS measurements were performed on a Bruker IPS 66V spectrometer operating at approximately 100 Pa. A mercury—cadmium—telluride (MCT) detector was used to collect spectra with a resolution of 2 cm i. The angle of incidence was 80° from the surface normal. A water-vapor-plasma-pretreated Ti mirror was used as the reference. For both sample and reference, 500 scans were collected. 

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