✦ LIBER ✦

Are atomic 3d-anisotropies important for chemisorption of hydrogen on cobalt?

✍ Scribed by Per E.M. Siegbahn; Ulf Wahlgren

Publisher: Elsevier Science
Year: 1991
Tongue: English
Weight: 425 KB
Volume: 177
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(91)90174-8

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✦ Synopsis

For transition metal atoms with open 3d-orbitals, the bond strength to other atoms can be expected to depend on the occupation ofthe different 3d-components. These 3d-anisotropy effects have ina recent paper been found to be very large, which should have significant consequences for the cluster modelling of chemisorption on transition metal surfaces. In particular, the description of transition metal atoms as one-electron systems using an isotropic effective core potential is, for this reason, strongly criticised. In the present study, the importance of the anisotropy of the 3d-shell has been studied for the case of diatomic CoH. Very different results are obtained compared to the previous study on this same system, and the reason for this discrepancy is analyzed.

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Oxygen interaction of CdS-based gas sens

Oxygen interaction of CdS-based gas sensors with different stoichiometric compositions was studied by X-ray photoelectron spectroscopy (XPS) and thermal-desorption mass spectroscopy observations combined with conductivity measurements. Three different types of film with different atomic ratios of Cd/S were used in the study of oxygen chemisorption in a low-temperature range between 300 and 570 K. Spray pyrolysis was used for the deposition of the films on glass substrates; XPS and energy dispersive spectroscopy of X-ray together with atomic force microscopy and scanning electron microscopy were used for the characterization of the composition and structure of the films. It was possible to distinguish different temperature ranges for the thermal desorption of the different adsorbed oxygen species. A comparison of the data from XPS and mass-spectroscopy observations with conductance measurements allows to conclude that metallic surface atoms are responsible for different interactions of oxygen species with CdS surfaces.

📂 Article 📅 1995 🏛 Elsevier Science 🌐 English ⚖ 379 KB