Magnetic properties of Fe and Tb in TbxFe1−x amorphous films studied with soft X-ray circular and linear dichroism

We have used linearly and circularly polarized X-rays to determine the magnetic properties of several Tb_xFe_1−x amorphous films. Absorption measurements on the M_4.5 edges of Tb and the L_2.3 edges of Fe allowed us to obtain information about the size and direction of local magnetic moments. Our results confirm that linear dichorism in rare earth M_4.5 edges can give useful information about both crystal field and magnetic effects.     

X-ray excited auger spectra (XAES) from chemisorbed species

Using X-ray excitation, well-resolved oxygen KLL Auger spectra have been obtained from chemisorbed layers of oxygen and carbon monoxide on Ru(001). These spectra are markedly different, while the spectrum of CO on Ru(001) is quite similar to the Auger spectrum from gaseous CO. The shift between the spectra of gaseous and adsorbed CO is much larger than for the corresponding XPS spectra, a fact understandable in terms of image charge screening. The use of XAES as a fingerprinting method for adsorbed species is recommended.     

Electron energy loss processes in X-ray photoelectron spectroscopy

A technique is established in X-ray photoelectron spectroscopy (XPS), using spectra emitted from successively evaporated metallic films, to distinguish between electron energy loss mechanisms identified as, respectively, extrinsic and intrinsic to the photoelectron excitation process. It is demonstrated that tailing on the high kinetic energy side of many XPS peaks is due to intrinsic processes, while the background emission at energies generally some 30 eV below the peaks arises from extrinsic processes. Plasmon energy-loss peaks are believed to contain contributions from both intrinsic and extrinsic processes.     

Photoelectron spectroscopic studies of adsorption of CO and oxygen on Ru(001)

XPS and UPS have been used for a detailed study of the adsorption and coadsorption of CO and oxygen on a clean Ru(001) single crystal. The measured substrate and adsorbate core level binding energies and valence levels are discussed. The O 1s XPS peak intensity has been used for kinetic studies of adsorption and coadsorption. Some studies of the angular dependence of adsorbate and substrate peak intensity ratios are presented. We also present data on the shifts of XPS peaks and changes in UPS spectra as a function of adsorbate coverage. The data are correlated with the results of earlier measurements with other methods.     

XPS,UPS AND XAES studies of the adsorption of nitrogen,oxygen, and nitrogen oxides on W(110) at 300 and 100 K: II. Adsorption of NO

The adsorption layers formed by exposure ofW(110) to NO gas at about 300 and 100 K have been investigated by XPS, UPS and XAES. At room temperature only dissociative adsorption takes place. At 100 K, the initial adsorption is also dissociative, but there is some indication of the formation of a transient NO species. Higher NO exposures lead to the formation of adsorbed N₂O, which then partly desorbs and partly dissociates before 150 K is reached. This shows that N₂O can be formed from N(ad) + NO. The relevance of our data to catalytic NO decomposition is discussed.