Resonant photoemission spectroscopy

Resonant photoemission spectroscopy with synchrotron radiation and surface... 

The comparison between theory and experiment was extended to various spectroscopies besides XPS, i.e. resonant photoemission spectroscopy. X-ray absorption spectroscopy (XAS) and, as we shall see in chapter 70 of this volume, also to bremsstrahlung isochromat spectroscopy (BIS). With one set of parameters it became possible to describe many experimental results, which in turn made it possible to extract new values of J and f. These values turned out to be quite... 

An average valence of v = 2.83 is derived for nearly stoichiometric TmSe from the lattice constant and v = 2.62 from the effective magnetic moment, Kobler et al. [16]. The value v = 2.62 is also deduced from the X-ray Lm absorption spectrum by Bianconi etal. [5, 17, 18], and v = 2.6 0.08 from bremsstrahlung isochromat spectroscopy (BIS) by Oh, Allen [19]. A value of v = 2.62 0.15 is obtained for the same crystal (Tm osSe, a = 5.715 A) by resonant-photoemission spectroscopy with use of synchrotron radiation in the soft X-ray region (70 to 200 eV) and constant-final-state technique (CFS), Oh et al. [41]. The valence v = 2.77 is obtained from the lattice constant and 2.46 or 2.58 from magnetic data between 77 and 300 K or 400 and 800 K, respectively, Holtzberg et al. [20]. These values are nearly confirmed for TmSe with a = 5.713 A... 

Resonant photoemission spectroscopy can give valuable information about the atomic orbital component of the state in the spectra. Figure 10 shows a plot of area intensities of the surface state induced peak for TaC(lll) as a function of the exciting photon energy. In Fig. 10, a cross section of the Ta 5d band observed in the photoemission spectra for poly-Ta (48) is also shown. The photoionization cross section for the surface state on TaC(lll) is resonantly enhanced at hv of 40 and 50 eV, as in the case for the Ta 5d band in poly-Ta. These enhancements of the cross section are well explained by the resonance process that proceeds via photon-induced excitation,... 

Thanks to the extensive literature on Aujj and the related smaller gold cluster compounds, plus some new results and reanalysis of older results to be presented here, it is now possible to paint a fairly consistent physical picture of the AU55 cluster system. To this end, the results of several microscopic techniques, such as Extended X-ray Absorption Fine Structure (EXAFS) [39,40,41], Mossbauer Effect Spectroscopy (MES) [24, 25, 42,43,44,45,46], Secondary Ion Mass Spectrometry (SIMS) [35, 36], Photoemission Spectroscopy (XPS and UPS) [47,48,49], nuclear magnetic resonance (NMR) [29, 50, 51], and electron spin resonance (ESR) [17, 52, 53, 54] will be combined with the results of several macroscopic techniques, such as Specific Heat (Cv) [25, 54, 55, 56,49], Differential Scanning Calorimetry (DSC) [57], Thermo-gravimetric Analysis (TGA) [58], UV-visible absorption spectroscopy [40, 57,17, 59, 60], AC and DC Electrical Conductivity [29,61,62, 63,30] and Magnetic Susceptibility [64, 53]. This is the first metal cluster system that has been subjected to such a comprehensive examination. 

More detailed information on the specific orbitals involved in bonding of the adlayer and the symmetry of the bonding site can be derived from angle resolved photoemission spectroscopy (ARPES). With excitation energies of less than 20 eV, the incident photons excite predominantly valence electrons. The valence electron resonances observed are characteristic of band structure of the substrate and the electron orbitals of the adspecies, whose energy is... 

Two-photon photoemission spectroscopy is known for its capability to reveal not only occupied but also unoccupied electronic density of states [10]. In this scheme, one photon excites an electron below the Fermi level to an intermediate state. A second photon then excites the electron from the intermediate state to a final state above the vacuum le vel. The photoelectron yields are strongly enhanced if the excitation photon energy is tuned to the resonance conditions, and the photoelectron spectrum reflects the electron lifetime in the intermediate states as well as their density of states. It is necessary to keep the employed photon energy below the work function of the sample, otherwise one photon photoemission signal becomes excessive and buries the 2PPE signals. 

X-Ray and Ultraviolet Photoelectron Spectroscopy Reference Energy Level Problem Resonant Photoemission ... 

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