The core level electrons in iron and its three oxides FeO, Fe3O4 and alpha -Fe2O3 have been studied by means of X-ray photoelectron spectroscopy. The main features of the spectra have been identified and electron binding energies have been measured. The Fe 2p peaks of the oxide spectra are broadened (FWHM approximately 4.5 eV) due to unresolved multiplet splitting, and shake-up satellites can be observed for both FeII and FeIII species. For all the samples studied the O 1s spectra consist of two overlapping peaks, one due to the oxide and a higher binding energy peak due to an adsorbed species. The higher binding energy peak was frequently dominant indicating a high degree of absorption on the oxide surfaces. The effect of argon ion etching on the surfaces has also been investigated and the results indicate that the analysis of surfaces by means of ion etching in conjunction with XPS can give misleading results.

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The stationary dense granular flow along an inclined plane has been studied in the present work. Several experimental results of the velocity profile published previously can not be described using conventional constitutive laws of continuum mechanics. Considering recent results revealing the diphasic behavior of granular medium under stress, we propose a new constitutive law relating the stress tensor to non-local functions of the velocity field and structural parameters of the material.