Local spectroscopic measurements

STM offers the possibility of performing local spectroscopic measurements (/ vs. V curves). These measurements can be performed in-situ and ex-situ. Ex-situ UHV conditions are however more appropriate to ensure the nonconductivity of the turmeling barrier between surface and tip. Such measurements on passive films formed on Ni and Cr should provide valuable information on the conductivity of the films. This is a promising perspective for the local characterization with high resolution of the electronic properties of passive films. On the subject of the relation between chemistry at the atomic scale and atomic structure, the STM results on the passive film formed on Ni also show promising perspectives for further characterization accurate bias-dependent measurements of the terraces of the NiO oxide should provide... 

The scanning tunnelling microscope (STM) is the most suited, and the most developed of the various SPMs, to perform local spectroscopic measurements. Discussion of STM techniques will constitute the bulk of this article. It also has the most restricted range of accessible substrates in terms of conductivity and roughness. The atomic force microscope (AFM) has limited spectroscopic capabilities but can image a wider range of samples. The near-field scanning optical microscope (NSOM) has excellent spectroscopic, but limited spatial resolution. These latter two SPMs are discussed at the end of this article. 

The hyperfine coupling constants of protons attached to a re-center can be determined by EPR/ENDOR spectroscopic measurements [15, 16] these coupling constants are proportional to the local spin densities at the re-centers as predicted by the corresponding atomic orbital coefficients of the... 

Below 0.07 h thermodynamic and IR spectroscopic measurements have shown that water adsorbed to the protein is localized at charged... 

Some essential discoveries concerning the organization of the adsorbed layer derive from the various spectroscopic measurements [38-46]. Here considerable experimental evidence is consistent with the postulate that ionic surfactants form localized aggregates on the solid surface. Microscopic properties like polarity and viscosity as well as aggregation number of such adsorbate microstructures for different regions in the adsorption isotherm of the sodium dedecyl sulfate/water/alumina system were determined by fluorescence decay (FDS) and electron spin resonance (ESR) spectroscopic methods. Two types of molecular probes incorporated in the solid-liquid interface under in situ equilibrium conditions... 

Unfortunately, the chemical composition tensor is not a directly measureable quantity. Instead, it must be deduced from indirect data. In the first place, spectroscopic measurements will usually be used to identify and quantify the chemical substances present. There may or may not be a one-to-one relationship between the intensity at one particular wavelength and the local concencentration of a particular chemical entity. In the second place, if the analysis is to be three-dimensional and non-destructive, the chosen range of electromagnetic... 

Another electronic property associated with aromaticity is magnetic susceptibility, which is determined by measuring the force exerted on the sample by a magnetic field. Magnetic susceptibility is closely related to polarizability and is different in the plane and perpendicular to the plane of the ring. It can be determined by various spectroscopic measurements, as well as by using an NMR spectrometer. It is observed that aromatic compounds have enhanced magnetic susceptibility, called exaltation (A), relative to values predicted on the basis of the localized structural components. 

In the CTAB-hexanol-water microemulsion system, the Ni(II) and Co(II) ions are not dispersed in the water core they are located in an envelope in the vicinity of the interface as was shown by and UV-Vis spectroscopic measurements. The Ni(II) local concentration is more important than the global concentration, with a correction factor given by [3]... 

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