Langmuir unit

Irving Langmuir United States surface chemistry... 

The XPS measurements were carried out on a VG ESCALAB Mark II electron spectrometer. TPD data was also collected on the same system using VG SX 200 Mass spectrometer. The Ru(OOl) crystal was fixed on a liquid N2 cooled manipulator and its temperature was measured by chromel/alumel thermocouple spot-welded on the side. The crystal temperature could be varied from 95 to 1500 K. The crystal surface was cleaned initially by Ar-ion bombardment and then annealed at 1200 K for about 20 min before flashing to 1500 K. The Sm was deposited by resistive heating of Sm sample inside the preparation chamber. CO doses to the crystal surface were measured in Langmuir units (1L=10 Torr-sec). A linear heating rate of 5 K/sec was applied for TPD measurements. 

Spectra similar to the top trace in Fig. 2.37, showing the characteristic distortion of the conduction band feature, were obtained after exposure of the iron foil to 2 L (L is the Langmuir unit, 1 L = 10" Torr sec) of oxygen at 300 K. The shoulder around 4 eV is indicative of the presence of ferrous ions. These are not normally formed in the initial phase of oxidation of elemental iron. The catalyst surface is... 

Adsorption studies on well-defined crystal surfaces, films, or flat surfaces were important to explain and correlate the interaction between molecules and surfaces of metals and supported metals. However, adsorption of molecules on crystal surfaces is usually performed under ultrahigh vacuum, free of impurities, and thus under ideal conditions. For example, if the molecule adheres at the surface after each collision, under vacuum at 10 torr, it forms a monolayer in 1 s, which corresponds to one Langmuir unit, or a monolayer. 

FIG. 1 Profiles of the heterogeneous surface generated by the procedure of Bakaev and Steele [81]. Each profile (except the upper one) is shifted downward with respect to the previous one by the unit of length. (Reprinted with permission from Langmuir 5 148-154, August 1992. 1992, American Chemical Society.)... 

A. Gentilini, C. Migliorini, M. Mazzotti and M. Morbidelli, Optimal operation of simulated moving-bed units for non-linear cliromatograpliic separ ations. II. Bi-Langmuir isotherm , 7. Chromatogr. 805 37-44 (1998). 

For nonlinear systems, however, the evaluation of the flow rates is not straightforward. Morbidelli and co-workers developed a complete design of the binary separation by SMB chromatography in the frame of Equilibrium Theory for various adsorption equilibrium isotherms the constant selectivity stoichiometric model [21, 22], the constant selectivity Langmuir adsorption isotherm [23], the variable selectivity modified Langmuir isotherm [24], and the bi-Langmuir isotherm [25]. The region for complete separation was defined in terms of the flow rate ratios in the four sections of the equivalent TMB unit ... 

Gentilini A., Migliorini C., Mazzotti M., Morbidelli M. (1998) Optimal Operation of Simulated Moving-Bed Units for Non-Linear Chromatographie Separations. II. Bi-Langmuir Isotherm, J. Chromatogr. A 805 37-44. 

All the fullerene-containing dendrimers reported to date have been prepared with a Cgo core but never with fullerene units at their surface or with Cgg spheres in the dendritic branches. We have recently started a research program on the synthesis of dendrons substituted with fullerene moieties. These fulleroden-drons are interesting building blocks for the preparation of monodisperse fullerene-rich macromolecules. In addition, they are also amphiphilic compounds capable of forming stable Langmuir films at the air-water interface. 

All the work we describe in this chapter was carried out in UHV on the rutile Ti02(l 1 0)1 x 1 surface. Exposures to vapors and gases are given in Langmuirs (L) where 1 L = 1.333 x 10 s mbar s. Coverages of defects or molecules adsorbed at the surface will be given in monolayers (ML), where 1 ML corresponds to the density of primitive surface unit cells. 

Data of the chemisorption of hydrogen on small copper particles were obtained by Ward (Proc Roy Soc London A133 506, 1031) in the units P, Torr, and V in cc/g STP. The plots show the Langmuir to be a better fit than the Freundlich. 

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