Metal surfaces compounds Electron energy loss

How then, can one recover some quantity that scales with the local charge on the metal atoms if their valence electrons are inherently delocalized Beyond the asymmetric lineshape of the metal 2p3/2 peak, there is also a distinct satellite structure seen in the spectra for CoP and elemental Co. From reflection electron energy loss spectroscopy (REELS), we have determined that this satellite structure originates from plasmon loss events (instead of a two-core-hole final state effect as previously thought [67,68]) in which exiting photoelectrons lose some of their energy to valence electrons of atoms near the surface of the solid [58]. The intensity of these satellite peaks (relative to the main peak) is weaker in CoP than in elemental Co. This implies that the Co atoms have fewer valence electrons in CoP than in elemental Co, that is, they are definitely cationic, notwithstanding the lack of a BE shift. For the other compounds in the MP (M = Cr, Mn, Fe) series, the satellite structure is probably too weak to be observed, but solid solutions Coi -xMxl> and CoAs i yPv do show this feature (vide infra) [60,61]. 

Future studies should emphasize the further application of spectroscopic techniques, AES, LEED, electron energy loss spectroscopy (EELS), and laser Raman spectroscopy to provide a more quantitative understanding of the interaction of sulfur compounds with metal surfaces. 

The special properties of rare earth metals and their compounds manifest themselves in some interesting electron energy loss phenomena. In the valence region the low energy (A 3-4 eV) one-electron transitions merit further study both by theory and experiment, while the surface divalency of Sm metal shows up in an anomalous plasmon-like excitation. The core region reveals a rich variety of quasi-atomic excitations with particularly strong resonance losses associated with 5p -> 5d and 4d - 4f transitions. These phenomena lead on the one hand to convenient surface valence monitors and on the other to non-dipole excitations unseen by other spectroscopies. 

In this review we consider how EELS complements other high-energy spectroscopies in elucidating the electronic properties of rare earths and their compounds. Section 2 reviews the interaction of electrons with matter, while section 3 surveys the experimental techniques of transmission and reflection EELS. Section 4 considers excitation of the outer electrons in rare earth metals and their compounds one-electron and plasmon losses show both continuation of bulk properties to the surface and modified surface environment. Section 5 looks at core excitations, which emphasise atomic rather than band-like properties, while section 6 suggests new applications of EELS which will enhance understanding of the idiosyncracies of rare earth systems that keep the rare earth community both intrigued and employed. 

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