Adsorption bandwidth

Spectral changes on adsorption are of three types appearance of inactive fundamentals (often coincident with infrared absorptions—see Table IX), shifts in Raman line positions for active vibrations, changes in relative peak intensities, and changes in half-bandwidths. The first three types of change have been reported for centrosymmetric adsorbates. 

To avoid the distortion produced by the shoulder, the bandwidth at Pt(lll) was analyzed at two-thirds of the peak height (AV2/3). The results are plotted in Fig. 54 as a function of potential. The band narrows as the potential increases, going through a minimum at 0.8 V. The dependence of the coverage on the electrode potential is presented in Fig. 55. This Figure shows a maximum adsorption at 0.8 V. Thus the band narrowing can be related to an increase of homogeneous lateral interactions as the adsorbate layer becomes more compact. The band asymmetry (see Fig. 47) indicates a random distribution of the adsorbed ions with low surface mobility [21]. 

The nonlocalized benzene adsorption on silica aerogel has been also inferred from the infrared spectrum of the surface silanol groups 43). It appears that the adsorbed molecules are executing a two-dimensional translatory motion with a free rotation in the molecular plane. The large bandwidth, mentioned above cannot be, however, ascribed to the mobility of the adsorbed molecule, since it is not appreciably affected by a lowering of the temperature down to 77 K, the shift of the spectrum being additionally increased by <30 cm. ... 

In nematic liquid crystals, the viscosity depends on the relative orientation between the shear gradient and the orientation of the nematic phase. Close to a surface, the orientation is usually governed by surface orientational anchoring [77]. Anchoring transitions, for instance induced by the adsorption of an analyte molecule to the surface [78], can therefore be easily detected with the QCM [79,80]. This reorientation induced by adsorption amounts to an amplification scheme the expected shift in the resonance frequency and bandwidth... 

The line width of the resonance-broadened adsorbate level is proportional to the square of the overlap energy and varies inversely as the bandwidth of the surface valence electron levels. The general form of the LDOS in the weak-adsorption limit... 

Biochemistry, Kiev, Ukraine) and water-soluble carbodiimide (V-cyclohexyl-V -(2-morpholinoethyl) carbodiimide methyl-/ -toluenesulfonate, CMC, Sigma) were used as received (Alexeeva et al. 2004). Adsorption experiments were carried out by shaking 0.2% aqueous solutions of individual solutes or proteins with CMC and a carbon sample at room temperature for 1 h. The adsorption of proteins was about 0.2 g/g. In these experimental conditions, unreacted CMC is hydrolyzed and washed out of the system (Alexeeva et al. 2004). Analysis of porous structure of SCN was done using nitrogen adsorption-desorption isotherm recorded at 77.4 K (Alexeeva et al. 2004). The H NMR spectra were recorded by means of a high-resolution WP-100 SY (Bruker) NMR spectrometer at the bandwidth of... 

The changes of the electron density of Ni surface atoms are shown before and after oxygen adsorption. One observes that the bandwidth of electron density on the surface atoms is less than that of the slab center atoms, which relates to the decreased coordination of the surface-atoms compared to the bulk. 

In addition to providing a separation where peaks have narrower bandwidths compared to those of a packed column counterpart, a properly prepared fused-silica capillary column, which has an inert surface (less potential for adverse adsorptive effects toward polar species), yields better peak shapes (i.e., bands are sharper with less peak tailing), which facilitates trace analysis as well as providing more... 

The width of a vibrational band provides additional information on adsorption. Typical bandwidths for adsorbed species on metal surfaces vary from a few cm to several himdred cm. Various mechanisms can contribute to them (Section 2.2.4) and their separation is sometimes not possible. The mechanisms responsible for the energy decay are not only interesting from the viewpoint of relaxation of excited states at the surface. The same decay channels determine the transfer of kinetic energy from the incoming particle into elementary excitations of the substrate and hence govern surface dynamics. 

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