Angle-integrated Photoelectron Spectroscopy Research Articles

Characterization of X-ray photo- and inverse photoelectron spectra of orthorhombic III?VII compounds in terms of norm-conserving pseudopotential calculation: Application to TII

Energy distribution curves for occupied and virtual states in orthorhombic thallium iodide through angle-integrated photoelectron spectroscopy are compared with the result of the total density of states calculation performed without any fitting parameters. The main spectral features are analyzed via charge density maps and generalized for other compounds of the TII-type structure.

Growth and structure of thin Au films on Ag(111).

The growth and the structure of thin Au films on Ag(111) were studied by measuring the angular distribution of core-level photoelectrons emitted at high kinetic energy using a two-dimensional display-type electron spectrometer. Additional information was obtained by angle-integrated photoelectron spectroscopy and by thermal desorption spectrometry of NO. We find, even at room temperature, intermixing induced by surface diffusion. This conclusion is corroborated by the study of Au films deposited on (1--3)-monolayer-high Ag films grown on Pd(111).

Investigation of the Electronic Structure of Oxocuprates by Photoelectron Spectroscopy

The oxocuprates Y2BaCuO5 and Bi2CuO4 the crystal structures of which contain discrete CuO5 and CuO4 units, respectively, have been investigated by angle integrated photoelectron spectroscopy. The Cu 2p core level and Cu L3VV Auger spectra are analysed within a simple cluster configuration interaction model. The experimental data and model parameters, namely the charge transfer energy Δ, the transfer integral T, and the correlation energy U as well as the main valence band features are similar as for oxocuprates with extended copper oxygen network.

Total reaction cross sections of electronic state-specified transition metal cations: V++C2H6, C3H8, and C2H4 at 0.2 eV

We describe a crossed beam experiment which measures total cross sections for reaction of electronic state-specified V+ with small hydrocarbons at well-defined collision energy E=0.2 eV. The V+ state distribution created at each ionizing wavelength is directly measured by angle-integrated photoelectron spectroscopy (preceding paper). Reactant and product ions are collected and analyzed by pulsed time-of-flight mass spectrometry following a reaction time of 6 μs. Tests of the performance of the apparatus are described in detail. Our experiment defines the reactant V+ electronic state distribution and the collision energy much more precisely than previous work. For all three hydrocarbons C2H6, C3H8, and C2H4, H2 elimination products dominate at 0.2 eV. We observe a dramatic dependence of cross section on the V+ electronic term. The second excited term 3d34s(3F) is more reactive than either lower energy quintet term 3d4(5D) or 3d34s(5F) by a factor of ≥270, 80, and ≥6 for the C2H6, C3H8, and C2H4 reactions, respectively. The 3d34s(3F) reaction cross sections at 0.2 eV are 20±11 Å2, 37±19 Å2, and 2.7±1.6 Å2, respectively, compared with Langevin cross sections of ∼80 Å2. For the C2H6 and C3H8 reactions, cross sections are independent of initial spin–orbit level J within the 3F term to the limits of our accuracy. Comparison with earlier work by Armentrout and co-workers shows that electronic excitation to d3s(3F) is far more effective at promoting H2 elimination than addition of the same total kinetic energy to reactants. Electron spin is clearly a key determinant of V+ reactivity with small hydrocarbons. We suggest that triplet V+ reacts much more efficiently than quintet V+ because of its ability to conserve total electron spin along paths to insertion in a C–H bond of the hydrocarbon.

Shape resonances above the Si 2p threshold in SiF4

Using monochromatized synchrotron radiation and angle integrated photoelectron spectroscopy, the Si 2p, Si LVV Auger, and F 2s cross sections have been obtained for SiF4 molecules in the gas phase between 116 and 150 eV photon energies. These cross sections and the Si 2p β value have also been calculated using the MS-Xα method. There is qualitative agreement between theory and experiment. Together with recent experimental and theoretical Si 2p cross sections from SiCl4 and valence band cross sections on SiF4, the two major resonances at 5 and 22 eV kinetic energies are assigned as t2 resonances. The valence band branching ratios are not affected by interchannel coupling above the Si 2p threshold.

Surface effects on core-level binding energies and valence in thulium chalcogenides

Vacuum-cleaved (100) surfaces of mixed-valent TmSe, divalent TmTe, and trivalent TmS were studied by high-resolution, angle-integrated photoelectron spectroscopy with the use of synchrotron radiation in the energy range $30\ensuremath{\le}h\ensuremath{\nu}\ensuremath{\le}110$ eV. In the topmost surface layers of TmSe and TmTe the $4f$ levels are found to be shifted to higher binding energies by 0.32\ifmmode\pm\else\textpm\fi{}0.04 and 0.41\ifmmode\pm\else\textpm\fi{}0.05 eV, respectively. In both TmSe and TmS the topmost surface layers are divalent. In the case of TmSe a separation of the ${\mathrm{Tm}}^{2+}$ $4{f}^{12}$ spectral feature into surface and bulk contributions allows a determination of the bulk mean valence $\overline{v}=2.55\ifmmode\pm\else\textpm\fi{}0.05$. While a shift of the Se $3d$ levels to lower binding energy is observed for Se atoms in the topmost surface layer of TmSe, no such shift can be resolved for the Te $4d$ levels of TmTe. The surface-derived divalent spectral features can be quenched completely in all three cases by exposure of the surfaces to submonolayer amounts of oxygen, resulting in the formation of trivalent surface oxides. Values for the electron mean free path $l$ are derived from the observed surface- and bulk-spectral intensities, with $l$ decreasing with decreasing electron kinetic energy down to \ensuremath{\cong}45 eV. Smaller singularity indices $\ensuremath{\alpha}$ of the Doniach-Sunji\ifmmode \acute{c}\else \'{c}\fi{} line shapes as well as smaller extrinsic losses are observed for photoemission from the divalent surface layers as compared to the bulk.

Valence-band structure of TiC and TiN

The valence-band structure of single crystals of titanium carbide (TiC) and titanium nitride (TiN) have been studied with angle-integrated photoelectron spectroscopy using ${\mathrm{He}}_{\mathrm{I}}$, ${\mathrm{He}}_{\mathrm{II}}$, and synchrotron radiation for excitation. The results are compared with the partial densities of states derived from an augmented-plane-wave band-structure calculation. Peak positions and widths agree fairly well, but the observed intensity modulations with photon energy cannot be interpreted by such a comparison.