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Highlights: [•] We describe new angle and time resolving electron analyzer with outstanding performance. [•] The transmission is more than 250 times higher compare to conventional hemispherical analyzer, no loss of energy resolution, time resolved studies are possible. [•] Details of operation modes and handling are discussed. [•] Review of studies performed is given as also an outlook of future possibilities. [•] Examples of new applications are discussed. [Copyright &y& Elsevier]

Abstract: We report on a novel type of photoemission detector, the Angle Resolved Time Of Flight electron energy analyzer (ARTOF 10k), which enables electronic band structure determination under measurement conditions that are ideal for radiation-sensitive samples. This is facilitated through the combination of very high electron transmission and wide accessible angular range in one geometry. These properties make the ARTOF 10k predestined to investigate specimens that strongly suffer from radiation damage during photoemission experiments under “standard” conditions, such as organic single crystals, as extremely low fluxes can be used while not compromising spectra accumulation times and signal-to-noise ratio. Even though organic single crystals are of increasing fundamental and applied scientific interest, knowledge of their electronic properties is still largely based on theoretical calculations due to major experimental challenges in measuring photoemission. In this work we show that the band structures of rubrene and tetracene single crystals can be obtained with unprecedented quality using the ARTOF 10k detector. The dispersion of the highest occupied band in rubrene is confirmed in accordance with an earlier report and we disclose the absence of notable dispersion for the highest occupied energy level on the surface of tetracene single crystals. [Copyright &y& Elsevier]

The use of the finite difference method to obtain a Taylor series expansion of a potential energy function for a subsequent calculation of the rovibration energies of molecules is considered. A method is proposed that allows the stability of a finite-difference scheme to be increased against the computational inaccuracy upon numerical expansion of a multidimensional potential energy function into a high-order Taylor series. The method is based on the successive elimination of calculated expansion coefficients of a higher order in calculating the lower-order coefficients by the finite difference method. The approach is illustrated for the example of the CO and H2S molecules. [ABSTRACT FROM AUTHOR]

Quantum numbers have been assigned in the theoretical spectra of three isotopologues of the water molecule: H2 16O, H2 17O, and H2 18O. The spectra were calculated by variational methods in the region 0–26000 cm−1 at a temperature of 296 K. For each molecule, the quantum numbers are assigned to more than 28000 levels. The quantum numbers are assigned to 216766, 210679, and 211073 spectral lines of the H2 16O, H2 17O, H2 18O molecules, respectively. The theoretical spectra with the assigned quantum numbers are available in the Internet. [ABSTRACT FROM AUTHOR]

We extend conventional laterally-resolved soft x-ray photoelectron emission microscopy to provide depth resolution along the surface normal down to a few angstroms. This is achieved by using standing-wave excitation. The sample is a Ag/Co/Au trilayer, grown on a Si/MoSi2 multilayer mirror, with the bottom Ag layer in a wedge profile. Tuning the incident x-ray to the mirror Bragg angle sets up a standing x-ray wave field in the multilayer and the trilayer wedge structure. We demonstrate the resulting depth resolution by imaging the standing-wave fields as they move through the trilayer wedge structure. [ABSTRACT FROM AUTHOR]

Using high-resolution angle-resolved photoemission, we observe a strong spin-dependent renormalization and lifetime broadening of the quasiparticle excitations in the electronic band structure of Ni(111) in an energy window of ~0.3 eV below the Fermi level. We derive a quantitative result for the spin-dependent lifetime broadening by comparing the scattering rates of majority and minority d states, and further show that spin-dependent electron correlations are instead negligible for sp states. From our analysis we experimentally determine the effective on-site Coulomb interaction U caused by Stoner-like interband transitions between majority and minority d states. The present results demonstrate the remarkable impact of spin-dependent electron correlation effects originating from single-particle excitations in a prototypical 3d transition metal, paving the way for further refinement of current many-body theoretical approaches. [ABSTRACT FROM AUTHOR]

The phase composition and local atomic and electronic structure of tin oxide layers have been studied by applying synchrotron X-ray absorption near edge structure spectroscopy. The linear combination analysis of the achieved results have been performed using first-principles calculated reference data for main tin-oxygen crystalline compounds. Our results suggest that proposed modelling approach successfully allows the reliable interpretation for Sn M 4,5 X-ray absorption near edge spectra caused by appropriate atomic structure reconstruction and phase transformation dynamics in thermally oxidized tin oxide layers produced by magnetron sputtering. [ABSTRACT FROM AUTHOR]

The transport properties of electronic devices made from single crystalline molecular semiconductors typically outperform those composed of thin-films of the same material. To further understand the superiority of these extrinsic device properties, an understanding of the intrinsic electronic structure and properties of the organic semiconductor is necessary. An investigation of the electronic structure and properties of single crystal α-phase perylene (C 20 H 12 ), a five-ringed aromatic molecule, is presented using angle-resolved ultraviolet photoemission, x-ray photoelectron spectroscopy (XPS), and field-effect transistor measurements. Key aspects of the electronic structure of single crystal α-perylene critical to charge transport are determined, including the energetic location of the highest occupied molecular orbital (HOMO), the HOMO bandwidth, and surface work function. In addition, using high resolution XPS, we can distinguish between inequivalent carbon atoms within the perylene crystal and, from the shake-up satellite structure in XPS, gain insight into the intramolecular properties in α-perylene. From the device measurements, the charge carrier mobility of α-perylene is found to depend on the device structure and the choice of dielectric, with values in the range of 10 −3  cm 2  V -1  s -1 . [ABSTRACT FROM AUTHOR]

A novel approach to the comprehensive study of the tin-oxygen compounds electronic structure and phase composition is reported. X-ray absorption fine structure relative to Sn M 4,5 edge and reflecting density of p- and f- electronic states in the conduction band for tin metallic foil, bulk SnO and SnO 2 oxides and tin oxide nanolayers have been obtained using synchrotron radiation. Same absorption edges of metallic tin single crystal, SnO, tetragonal and orthorhombic SnO 2 have been ab initio calculated for the first time. Peculiarities of the experimental spectra fine structure transformation have been precisely analyzed and connected with changes in the surface composition of materials under study. The technique of materials composition semiquantitative estimation in tin-oxygen system by means of linear combination fitting of the calculated spectra was discussed. [ABSTRACT FROM AUTHOR]

The mass sensitivity of the vibration-rotation-inversion transitions of H316O+, H318O+, and D316O+ is investigated variationally using the nuclear motion program TROVE (Yurchenko, Thiel & Jensen). The calculations utilize new high-level ab initio potential energy and dipole moment surfaces. Along with the mass dependence, frequency data and Einstein A coefficients are computed for all transitions probed. Particular attention is paid to the Δ|k| = 3 and Δ|k - l| = 3 transitions comprising the accidentally coinciding |J, K = 0, ν2 = 0+〉 and |J, K = 3, ν2 = 0-〉 rotation-inversion energy levels. The newly computed probes exhibit sensitivities comparable to their ammonia and methanol counterparts, thus demonstrating their potential for testing the cosmological stability of the proton-to-electron mass ratio. The theoretical TROVE results are in close agreement with sensitivities obtained using the non-rigid and rigid inverter approximate models, confirming that the ab initio theory used in the present study is adequate. [ABSTRACT FROM AUTHOR]

Highlights: [•] We developed an experimental end station for time- and angle-resolved X-ray electron spectroscopy. [•] The instrument can operate in combination with synchrotron radiation, VUV Helium discharge source or table-top high-harmonic laser sources. [•] Band mapping in solids is possible with unprecedented rapidity. [•] Electron–electron coincidence spectroscopy is performed at higher data collection rate (due to improved transmission) and with improved energy resolution. [Copyright &y& Elsevier]

We report a Rashba spin splitting of a two-dimensional electron gas in the topological insulator Bi2Se3 from angle-resolved photoemission spectroscopy. We further demonstrate its electrostatic control, and show that spin splittings can be achieved which are at least an order-of-magnitude larger than in other semiconductors. Together these results show promise for the miniaturization of spintronic devices to the nanoscale and their operation at room temperature. [ABSTRACT FROM AUTHOR]

We have studied the electronic structure of EuFe2As2-xPx using high-resolution angle-resolved photoemission spectroscopy. Upon substituting As with the isovalent P, which leads to chemical pressure and to superconductivity, we observe a nonrigid-band-like change of the electronic structure along the center of the Brillouin zone (BZ) in the form of an orbital and kz-dependent increase or decrease in the size of the hole pockets near the Γ-Z line. The diameter of the Fermi surface cylinders at the BZ corner which form electron pockets, increases at K and changes in a nonmonotonous way at X. This is in stark contrast to p- and n-type doped iron pnictides where, on the basis of ARPES experiments, a more rigid-band-like behavior has been proposed. These findings indicate that there are different ways in which the nesting conditions can be reduced causing the destabilization of the antiferromagnetic order and the appearance of the superconducting dome. [ABSTRACT FROM AUTHOR]

Abstract: A new technique for the detection of X-ray absorption in multilayer structures, Capacitance Transient X-ray Absorption Spectroscopy (CapTXAS), has been developed. CapTXAS technique utilizes the fact that excess carriers generated in the semiconductor structure under the X-ray excitation can be captured with deep level electronic states at the structure interface(s) within the space charge region of the Schottky-diode giving rise to the diode capacitance changes. Short periodical refilling electric pulses are applied to the structure to define the initial trap occupancy and the first derivative of the capacitance transients after the bias voltage recovery is measured. We installed this technique at BESSY Russian–German Beam Line and applied to the measurements on two test semiconductor structures: Au–/nickel–phtalocyanine/–silicon and Al-bonded silicon wafer. [Copyright &y& Elsevier]

Abstract: The valence electronic structure of a series of molecular films containing ruthenium polypyridine complexes has been investigated by photoelectron spectroscopy (PES) at high kinetic energy (HIKE) using hard X-ray. The experiment shows the possibility to experimentally probe the metal contribution to the valence spectra in a bulk sensitive mode. Specifically to directly follow the Ru 4d contribution to the highest occupied molecular orbitals of such complexes. The experimental spectra are accurately modeled by DFT calculations only if a crystal structure environment is taken into account showing the importance of intermolecular interaction for modeling the electronic structure of such complexes. [Copyright &y& Elsevier]

In this work, we present the CoESCA station for electron–electron coincidence spectroscopy from surfaces, built in a close collaboration between Uppsala University and Helmholtz-Zentrum Berlin at the BESSY II synchrotron facility in Berlin, Germany. We start with a detailed overview of previous work in the field of electron–electron coincidences, before we describe the CoESCA setup and its design parameters. The system is capable of recording shot-to-shot resolved 6D coincidence datasets, i.e. the kinetic energy and the two take off angles for both coincident electrons. The mathematics behind extracting and analysing these multi-dimensional coincidence datasets is introduced, with a focus on coincidence statistics, resulting in fundamental limits of the signal-to-noise ratio and its implications for acquisition times and the size of the raw data stream. The functionality of the CoESCA station is demonstrated for the example of Auger electron–photoelectron coincidences from silver surfaces for photoelectrons from the Ag 3d core levels and their corresponding MNN Auger electrons. The Auger spectra originating from the different core levels, 3 d 3 ∕ 2 and 3 d 5 ∕ 2 could be separated and further, the two-hole state energy distributions were determined for these Auger decay channels. • Auger electron–Photoelectron Coincidence spectroscopy (APECS) from surfaces. • Disentangling Auger decay spectra from Ag 3d core level photoionisation. • New synchrotron end station for user operation at BESSY II. [ABSTRACT FROM AUTHOR]

Generally, the lack of long-range order in materials prevents from experimentally addressing their electronic band dispersion by angle-resolved photoelectron spectroscopy (ARPES), limiting such assessment to single crystalline samples. Here we demonstrate that the ARPES spectra of azimuthally disordered transition metal dichalcogenide (TMDC) monolayers with 2 H phase are dominated by their band dispersion along the two high symmetry directions Γ-K and Γ-M. We exemplify this by analyzing the ARPES spectra of four prototypical TMDCs within a mathematical framework, which allows to consistently explain the reported observations. A robust base for investigating TMDC monolayers significantly beyond single crystal samples is thus established. The complex nature of polycrystalline materials mean that characteristics such as their electronic band structure can be more challenging to interpret than their single crystal counterparts. Here, the authors present a framework based on angle-resolved photoemission spectroscopy to reveal the band dispersions for azimuthally disordered transition metal dichalcogenide polycrystalline monolayers. [ABSTRACT FROM AUTHOR]

We study the underlying chemical, electronic, and magnetic properties of a number of magnetite-based thin films. The main focus is placed onto Fe3O4(001)/NiO bilayers grown on MgO(001) and Nb-SrTiO3(001) substrates. We compare the results with those obtained on pure Fe3O4(001) thin films. It is found that the magnetite layers are oxidized and Fe3+ dominates at the surfaces due to maghemite (γ-Fe2O3) formation, which decreases with increasing magnetite layer thickness. For layer thicknesses of around 20 nm and above, the cationic distribution is close to that of stoichiometric Fe3O4. At the interface between NiO and Fe3O4 we find the Ni to be in a divalent valence state, with unambiguous spectral features in the Ni 2p core level x-ray photoelectron spectra typical for NiO. The formation of a significant NiFe2O4 interlayer can be excluded by means of x-ray magnetic circular dichroism. Magneto-optical Kerr effect measurements reveal significant higher coercive fields compared to magnetite thin films grown on MgO(001), and an altered in-plane easy axis pointing in the ⟨100⟩ direction. We discuss the spin magnetic moments of the magnetite layers and find that a thickness of 20 nm or above leads to spin magnetic moments close to that of bulk magnetite. [ABSTRACT FROM AUTHOR]