Oxygen adsorbed nickel

Calvet microcalorimeters are particularly convenient for such studies. Figure 19 show s, for instance, the evolution of the differential heat of adsorption of oxygen, measured at 30°C with a Calvet calorimeter, as a function of the total amount of oxygen adsorbed on the surface of a sample (100 mg) of nickel oxide, NiO(200) (19, 73). The volume of the first... 

As oxygen adsorbs on the nickel surface, the intensity of the diffraction pattern from the nickel lattice decreases, because of the low penetrating power of the electrons and the high scattering power of the adsorbed oxygen. In Figure 2 are shown certain characteristic diffraction beams in the form of colatitude curves. 

As oxygen adsorbs on the nickel surface, the intensity of the diffraction pattern from the nickel lattice decreases because of the low penetrating power of the electrons. This rate of decrease with increasing exposure is approximately the same for an ion-bombarded surface which has been well annealed as for one which has received a small anneal. However, the diffraction patterns from the gas-lattice structures on the surface with the small anneal are much more intense than those from the gas-lattice structures on the well-annealed surface because of the different defect densities in the two cases. If the extinction of the pattern from nickel were caused by the presence of the gas-lattice structures, one should expect a greater rate of extinction for the surface having a small anneal. Since this is not the case, the major part of the ex-... 

Figure 1.19 The structure of oxygen adsorbed on a close-packed nickel surface together with the corresponding LEED pattern...

STS has also been applied to a study of the unoccupied surface states of graphite [249], hydrogen-like image states on clean and oxygen-covered nickel and on gold epitaxed on silicon (111) [266], [267], the superconducting energy gap in NbsSn [268], the electronic structure of the InP (110) surface [245], and copper phthalocyanine adsorbed on Cu (100) [269]. 

C. Benndorf, C. Ndbl, and T. E. Madey, Water adsorption on oxygen-dosed nickel (110) formation and orientation of adsorbed hydroxyl, Surf Sci. 138 292 (1984). 

The p(2x2) 0/ Ni(lll) system is reconstructed with a twist deformation of three of the top layer nickel atoms and a vertical displacement of all of the atoms in the top layer of the unit cell (LEED [90Gri]). The oxygen coverage is 0.25 ML. A schematic view of the structure of the p(2x2) overlayer is reported in Fig. 44. The oxygen lifts three of the nickel atoms away from their original bulk positions, while the fourth relaxes towards the second layer Ni atoms. The surface phonon dispersion measured by HREELS is reported in Fig. 45. Five optical modes are observed. The modes at 67 and 71 meV are assigned to oxygen adsorbate vibrations, while the lower modes lie within the bulk bands. The open (filled) circles... 

Resolved Photoemission from Oxygen Adsorbed on Nickel (100) in the p (2 x 2) Structure, Solid State Communications 25 (1978), p. 93-99. 

Schlatter et al. found that their data with copper chromite agrees better with 0.7 order for CO concentrations (53). For crystals of nickel oxide and chromium oxide, Yu Yao and Kummer have found that the kinetics depend on CO or hydrocarbon around 0.55 order and depend on oxygen around 0.45 order (79). Hertl and Farrauto found evidence that CO adsorbs on copper as a carbonyl group, and adsorbs on chromium oxide as a unidentate carbonate. They found that the kinetics depends on CO to the first order, and depends on oxygen to the zero order (80). 

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